I think one of the draws of a basic isekai story, is a power fantasy. As someone who will never experience these sorts of things, it's a fun way to escape reality, with the MC cast as the perfect stand-in for yourself. This is the first point at which Mushoku Tensei (MT from here on out), differs. It openly challenges the stereotypical "first step", so to say, of an isekai. Besides truck-kun, the manga and LN both diverge in its open negative portrayal of NEETs and Shut-ins, predominantly using this negative connotation as a factor for character development.
I tend to measure how well manga are written by the ability to entertain. As with any media form, the only way to succeed is to create a dedicated audience. I think that MT does this in a number of different ways. Firstly, the strength of this manga comes from, generally speaking, the characters. They're real people, with real emotions, flaws, and personalities. They're human in a way in which many isekai characters are not. Eris has to grapple with her own insecurities. Rudeus is dealing with the trauma created by his previous lifestyle. Paul is a womanizer, and an alcoholic. Roxy has family issues and an apparent hard-on for 10-year-old Rudeus (that one isn't a problem in the manga but still). While having blank-slate characters is all well and good, characters that are human build investment. The blank characters simply fall flat when compared to the way the manga is able to create human characters. Their choices may not be the right ones. Their choices may be stupid given our omnipotent presence and obviously superior judgement skills (I know we all feel that way). But, they are believable. They are never out-of-character, their decisions feel natural and flow from the heart, as opposed to the plot. This is what MT does so well. It builds investment in its characters, where most of us can't actively empathize with the solution Rudeus is in. Most of us don't live that life, but, we can understand where he's coming from, and that's what makes us care. We want to see these characters happy, and we want them to achieve the goals they want, even though they may not be our goals, because we UNDERSTAND. I think beyond the general plot, and the basic art style, this is what fuels viewership of this manga.
Speaking of which, let's talk for a bit about story and art. The story itself is fairly standard fare until the big white happens. It's classic OP anime character shenanigans, intelligence and all, and while the character is set up to be powerful, he's not the complete balls to the wall BAMF that some other isekai use (~ahem~ In another world with my smartphone ~ahem~). The first ~20 chapters establish a couple of key things. Firstly, his power level, secondly, his relationships with the characters around him, and finally, what his goal is (more or less). Then, as obviously the big phenomenon happens, everything is bent out of shape. This is where the story actually picks up. It's a very unusual concept, certainly original, and interesting, The gripe I have with the story and why it scores lower than the characters, is due to one flaw. The pacing. It's all over the place. This may be something the LN does better, but I had no concept of time while reading it. I will simply follow along on their adventures, and boom, 3 YEARS HAVE PASSED. I had to rely on the text telling me how much time had passed because to me, the events happening feel like a number of days, while in reality it's been months. The story does a poor job of knowing when time speeds up and slows down, and thus, signposting was the only way I could understand any of this. The art is good. The characters are unique and diverse-looking, generally, it was inoffensive, and was pretty great during certain scenes. Especially emotion, as the art of Eris crying did very much remind me of DomeXKano, and we all know what a minefield of mixed emotions that manga drives you through. I think the art does genuinely do the job and shines in a few places.
In the end, I thought it was a very good story weighed down by shotgun pacing, the art was very good, if not particularly genius, and very human characters. The investment in its characters, the genuine danger the plot drives them through, and the unconventional story combine for a very enjoyable anime I would recommend to fans of the isekai genre.
