In my opinion, Black Clover is a fairly overrated anime which has major issues in many different aspects of its production. Having watched it until it's completion it was a huge disappointment for me, considering that the original idea sounded intriguing. I've also heard the manga is much better (though at the time of writing I've not read it), so I'm rather miffed that they studio put this low a quality into what probably was a fairly decent series.
Worldbuilding: 2/10
While the writers of Black Clover did create a somewhat extensive world to work with especially when it comes to the magic system, the application was overall underwhelming.
The entire universe only consists of four countries, and the relations between them tend to be very basic. We know the Clover Kingdom and the Diamond Kingdom are at war, and we know that the spade kingdom is struggling for resources, but we've never really gotten to see enough to completely understand why they would be willing to literally abuse and mutilate children in order to gain more military power. Blatant terrifying acts like that only hold weight if we are able to really spend time with some exposition about the country as a whole. That being said, we only learn about the Heart kingdom extremely late in the series, and we know perhaps even less about it than the Diamond kingdom. Why would the Heart Kingdom isolate itself if it objectively had more military might than probably the Heart and Clover kingdom combined. Granted that it seems to be run over an absolute monarchical rule, It doesn't make sense that all of the ruler's have been benevolent for some reason. That goes against the most blatant weakness of authoritarianism, which is that it is extremely prone to corruption. And the spade kingdom is barely mentioned at all until the very end of the season when it becomes the capitol of the dark triad.
As for the magic system, although it might appear to be extensive at a first glance, it's only complex at face value. Yes, there are different types which can counter each other (which in and of itself is a rather basic concept of a magic system which includes types), but the overall adaptability and application of each power is limited heavily on a person's grimoire. The extent to which they can use their powers and their special abilities are specifically limited to spells written in the grimoire. And their powers are only ever used at face value, no one is stretching exactly how far they can take their powers and using that to develop new ones. And although we see people 'train' or try to develop emotionally, the correlation to them getting a new spell is non-dependent. The character isn't developing their powers themselves, the new spell just appears out of thin air, and the character had no say whatsoever in what the power does. It's extremely uncreative and really does a magic system injustice, especially considering the potential it had to be good. Imagine if through training you could write your own spells in your book. Or if we saw powers being adapted in uncanny ways like Finral's portals being used to easily accelerate objects.
Plot: 1/10
The plot in the anime is rather generic and cliched especially for shonen which is already oversaturated as is. We've seen it so many times, a character doesn't have any powers, but then it turns out he either has some huge innate power, or inherits the power from something. Examples of this are Fire Force, My Hero Academia, I could go on. Some of the arcs were interesting, personally I enjoyed the fairy arc with Licht the most out of all of them. Honestly if it had ended there my score might have been higher. However with the introduction of the demons as antagonists the quality just went down. The demons became an escape from proper pacing and power scaling.
The pacing of the series itself is fairly decent up to the end of the first demon fight. I'm saying that purely in terms of new plot though. The amount of flashbacks and narration is an obvious attempt at trying to stretch the length of the series as much as possible. new plot doesn't start until 6 minutes in most episodes. If you count the outro as well that's about 8 minutes of the show doing absolutely nothing. considering 24 minutes episode times that's only a 16 minute actual episode length, which is ignoring that flashbacks in some episodes might take around half of that time (especially nearing the end of the anime).
Before the last arc of the anime (dark triad), the timeline skips an entire 6 months, during which time most of the characters have apparently become ridiculously overpowered. And then we're thrown suddenly into fights with a ton of new enemies which we had not seen before and have no emotional connection towards, and somehow they are just as powerful, or even more powerful than asta and the commanders. Not to mention, 3 episodes from the end a new mentor is introduced.
However my biggest gripe, is that the series ended.... WITHOUT THE FINAL FIGHT. Yes, I know it's getting a movie sequel. But still. A 170 episode buildup, and we get a corny ending about how they are going to get stronger and defeat the dark triad. Yes, I'm getting a little emotional here, but seeing the ending really upset me. It really upset me.
Characters: 1/10
I of course don't mean to say that all of the characters are bad, but unfortunately most of them are extremely 1 dimensional and based on cliches. Asta has one goal, and one goal alone. He's unrealistically optimistic, and he never goes through any substantial character development. Most of the time, the show portrays him as completely perfect. Maybe not in physique, but in character. People who throw any actually valid criticism at him about his mantra of 'never giving up', even when realistically he ought to have died several times over are generally thrown under the bus at some point. That's essentially the definition of a Mary Sue. Why would I like Asta when he essentially is constantly screaming, and believes that if he swings his sword faster, and rushes at his enemy in a slightly different way than before, and for some reason the writers say that it ought to work. There's no way people would enjoy Asta if he was a person in real life.
Yuno isn't that much better. He has the exact same goal as Asta, and the two are said to be in a rivalry over it, Yet we don't actually see much of a rivalry. Maybe this is a mistranslation of the original Japanese meaning, but rivalry generally implies conflict and a distaste towards the rival which we don't see. Another problem is Yuno's power scaling generally happens off screen, so we generally don't have any emotional connection with him. This is further amplified by the fact that he's portrayed as being stuck up and somewhat elitist. And I don't want to spoil the fine details of the plot but there are some very very cliche explanations for Yuno's past which is a letdown because it was hidden from us for most of the series.
As for the Dark Triad, their personalities are probably the most one dimensional out of all the villains in the series. They embrace evil for the sake of evil. One is a megalomaniac, one is a narcissist, and the last is a masochist. If you've seen it you probably already know which characters I'm referring to. Their underlings have the same one-dimensional personalities (often time relating extremely obviously to the actual power they have like the tongue dude being a pervert). But the largest problem is we only get to see them extremely late in the series. They don't have time for any character development at all, Especially when compared to Licht.
That being said, I'd say Licht was my favorite character because he at least seemed to have more than one motivation for his actions and ideals, and you couldn't just lump him in there with the notion that he was completely evil. Although, the same can't be said for his minions.
There are plenty of other side characters I could talk about as well, but the cast is so broad that it would be impossible to get into all the details in this already long review.
Art/Animation: 3/10
When the anime tries, it does well. Still scenes look pretty decent, the animation quality is nice. However, in the fight scenes, where arguably the most effort ought to be put in, the quality greatly diminishes. Lazy fails to describe it enough. Ground ceasing to have any texture whatsoever. Characters loosing some discernable features occasionally. It completely breaks the atmosphere of the fight scenes. This problem becomes much worse in the later arcs of the anime.
Sound: 5/10
Of all things, the sound gets rated the highest I'd say. Mainly because the music wasn't that bad. Sure it was somewhat generic in terms of compositional style, but for the most part the music matched the mood of the scenes, and the production quality was up to standard. It's forgettable, but it serves its purpose.
However the voice acting for asta in particular wasn't that great. I know a lot of other people have mentioned this but his screaming is just ear-grating and there is no real point to it at all.
Overall: 3/10
Unfortunately I just can't recommend this show to a new viewer. It has extensive flaws in many aspects of production that just ruins its potential. It relies heavily on cliches, and generic plot devices to drive the story forward, and the ending is extremely anti-climatic. If you decide to watch please keep these points in mind. Don't go into it expecting an innovative shonen or a great plot.