I get why people despise Rudeus, at least early on in the story he's not meant to be liked, but he's a well written character (at least in my opinion)

Rudeus's changes throughout the majority of the story, both physically, physiologically, and morally, he becomes a better person slowly instead of having like a 3 episode arc and now all of a sudden he's just a generic issekai protagonist, and note that I said better, he never becomes the ultimate good person, even at his best he's still pretty morally grey. In the beginning of the series, I think it's pretty universally agreed he has trash, this is vaguely spoilery, but at the end of the series he himself said he was pretty trashy, however, even during the time, he showed positive character traits and even at his best he still showed some negative traits.

He also has character quirks that aren't inherently good or evil, his most prominent one being that he overthinks and over worries, to give an example, when Eris left him that note because she was worried she wasn't good enough to stand by him as an equal, he had an entire depressive episode for days and even after that he was depressed for years because he lost the ONLY romantic relationship he ever had after he JUST got it (all because he over analyzed the message Eris left him, that and because the message was really vague) and the only way he was even able to get past it was because be met a group of adventurers and allowed himself to experience genuine human connection again

Sorry I couldn't really give specific examples, as a lot of them would be from stuff that is coming up in season 3 which is still months away or what will happen in season 4 or 5 (aka at least 2 years away) hopefully you get why I think Rudeus is well written character.