Mushoku tensei is probably the best isekai to date, i have very few issues with it other than some of its weird world building, like the several different groups of titles given to certain characters that get really confusing and aren't ever explained that well, the story also slows down a lot after homeboy settles down but it actually does effectively convey how much time has passed and how different characters/places have changed.
I do think it embodies a problem that a lot of isekai have: The lack of any inner drive for the MCs, you see it in a lot of isekai, the MC's only "drive" to do anything is "I want to live a nice life with my family/friends/country", the only reason the plot happens is because someone else wants to fuck with the MC, aka; an external conflict.
MCs don't really have any goals or motivations and if they do it's just the cliché "I wanna get stronger", I don't blame MT for using this trope since it does it better than anyone else, but it does get tiring.