I enjoyed it. It's quite good... but that's judging by the standards of light novel adaptations where the hero's ridiculously overpowered and there's no dramatic tension in anything he does. The outcome of any fight is a foregone conclusion, for instance, and of course he'll end up with all the girls attracted to him. The whole thing's just a succession of "Make Hero Look Cool" checkboxes.
That said, though, it's not empty slice of life fluff. The hero (Rio) gets tortured, bullied and forced to quit school. He's an orphan from the slums whose mother got murdered in front of him. He saves a princess in ep.1 and ends up being given permission to attend school, but his aristocratic classmates resent this and treat him as scum. Similarly, the setting's more detailed than you'd expect, so for instance the language barrier isn't handwaved and at first Rio's illiterate. There are rival nations and nasty politics. Beast people are enslaved and worse. Power is there to be abused and anyone in a noble family is almost certain to be a total bastard.
Even Rio himself isn't one-dimensional. He's so rigidly polite that close friends might ask him to be less formal with them. When aristocrats bully him, he seems to think that their superior status makes this fair and normal. He's normally a mild-mannered saint... but there's a scene where he completely loses it on catching a would-be rapist. He nearly beats the man to death.
As I said, I enjoyed the show. But it does have issues:
1. The four books that were adapted into this season are very different in setting and supporting cast. Every three episodes, Rio travels to a different country where he'll live for at least a year. This means constantly abandoning his new friends. Sometimes this is dramatic (e.g. Celia), sometimes you don't care (e.g. the extremely underwritten Sayo) and sometimes it's annoying (e.g. Latiifa). She's the character I cared about the most. Book Two (eps.4-6) is the strongest, thanks to Celia and her horrifying backstory. She's a child, yes, and so for Rio to keep travelling with her could be called child endangerment... but she's also a Rio-level fighter with super-speed and assassin training. The show actually doesn't want her around partly because she's too good at fighting and would steal some of the spotlight from the Designated Cool Protagonist. She also really, really wants to stay at Rio's side and I didn't buy the show's justifications for him continually leaving her behind.
2. The characterisation isn't deep. The scumbags in Book One (eps.1-3) are so generic and interchangeable that I'd completely forgotten which one was which when they returned in Book Four (eps.10-12). I couldn't remember what Charles Arbor had done to earn his villain treatment, for instance. (Answer: he's the idiot who tortured Rio for tiresomely stupid reasons in ep.1.) The girls tend to be defined by their reason for falling in love with Rio. The characterisation's usually enough to support the story at hand, but it doesn't go deeper.
3. The coincidences, revelations, power-ups, etc. to boost Rio can be almost comical. By the end, he's practically Superman... and yet this season ends on a pseudo-cliffhanger for Season 2. How much stronger is he going to get?
4. I could have lived without the harem angle. By the end, the girl count (and more importantly the "Apparently Fated To Be With Rio" girl count) has reached a level that suggests I'll probably find Season 2 annoying.
5. The show isn't always as clever as it thinks it is. When Rio learns that a human-shaped spirit is living inside him, he doesn't suggest that this might be Haruto Amakawa, the Japanese college student who appeared in his head one day. (Isekai heroes are a thing in this world and indeed the later novels apparently introduce "heroes" who are negative deconstructions of isekai hero tropes.) The show has something else in mind for that inner spirit, as it happens, but it's still illogical for Rio not to raise the possibility. Similarly, on finding a city where people eat pasta and call it "pasta", Rio doesn't think to investigate in case this came from another isekai character. He just takes it for granted, because lazy anime fantasy settings these days are often full of real-world food like pizza and sandwiches.
All that said, though, I did enjoy the show. It's ambitious. It's portraying a broad world that can get extremely nasty. Rio is a fantasy wish fulfilment figure, yes, but he's a likeable one (outrageously polite) and it's satisfying to see him unleashed on people who deserve it. A hypothetical Season 2 might yet resolve the harem situation in a satisfying manner, although I bet it doesn't. I'm glad I watched this.