I am not a big fan of Stan but I can see reasons why some may like him. He might be just the kind of guy some of us were or even still are, playing adult games and wanking much too often thinking about those naughty girls. So some may identify with him

. Think about it!
That's the intended appeal, for sure, but its badly implemented. Stan is on standstill for 11 chapters, then Lena suggests him to work out and encourages him by making with him out. Thats all the development and its as rushed as it is unconvincing.
If he started poorly in chapter 1, but got rejected by Lena right in say chapter 2, then spend the entire game picking himself up, step by step motivating and redeeming himself, it could work. Instead he is a nothing burger for 11 chapters until the incel confession he could've had at the beginning of the game. He has the same low self-esteem as Holly, but Holly makes far quicker and far more often moves on Ian and changes much more fluid and rapidly.
This was much better done with Eric in the first game, who also starts as a whimp, but progresses significantly better paced to the either cuck or chad path, despite not even having much screen presence.
In summary, Stan lacks both quantity and quality in writing. Just being a mirror for the average loser nerd isn't enough, you want that projection of yourself to either succeed (power fantasy) or fail (self-loathing confirmation). Stan isn't managing either of them greatly.