Let's go over the biggest problem: it's rushed like hell.
How rushed? Well...
Imagine if you had to adapt JoJo part 5 into 13 episodes...
Or HxH into 24 episodes...
Or FMA into 16 episodes...
Or... Well, you get the idea.
The original manga is 43 volume long. This anime is 36 episode.
This means that even if they adapted a volume per episode, it wouldn't do it. So they had two choices: either cut whole volumes or cut small content. They choose both.
Now to the problems that this causes: it's a mess.
There is barely any characterization for the characters we are supposed to care about, and the character development is so sudden it makes no sense. Characters will do things that they would normally never do for no reason at all because of it.
The story also just keeps jumping nonstop from one point to another, dramatic moments will happen with no build-up whatsoever and sad songs will play at a sad moment that no one cares about.
Technically speaking, it's also ugly. Character movements are too stiff, actions scenes barely have any action and are just static shots of a character delivering an attack. Excessive post-effects are added to some scenes and they also look ugly (for example, the white bloom that is present through the whole hospital arc fight).
It also manages to have a terrible directing and editing. Characters will just stand somewhere or walk while talking with nothing happening on-screen (as in episode 4 when two character are talking on the side walk), some cuts are TOO SUDDEN (episode 13 cuts to the opening all of sudden almost as if it wanted to make a cliffhanger, but it just made it worse) and the narrative in general is really just too much simplified.
As I re-write this review, all of my points are still valid and the show has only gotten WORST. It's downright offensive to the viewers and to the original material.
There's not much too say. It's just a really bad and insulting show. A real waste of good source material.
TL;DR do yourself a favor and read the great manga
