I think the reason Mushoku Tensei sticks with people longer than most isekai is that nobody in it is finished growing. Rudy starts out about as incorrigible as an isekai lead gets, Paul is a mess of a father, Eris can't control her temper, and the show lets every one of them fall on their face before they get better. A lot isekai hand you a hero who already has it figured out or learns that fast. Mushoku makes you watch the work, and that's why the payoff hits harder. #MushokuTensei