1. Young, stupid male MC.
2. Peeking and 'step by step' escalation in sexual acts usually starting with a handjob, next week maybe a blowjob.
"Young" is fine. But "Smart" would be a decided improvement. E.g., the MC decides he wants to accomplish X, Y, Z. He does some research, makes a plan, starts executing it. Some of things he tries work well, some don't, as this happens he refines his approach. He also starts to anticipate problems before they happen, so starts planning ahead to deal with them.
My least favorite "meta trope" is the "one size fits all" approach to game development--just throwing in fetishes to try to draw in as many people as possible. Combined with the "don't reinvent the wheel, stick with what works" approach, you wind up with dozens of games in a contemporary urban/suburban family household, or an apartment building full of milfs and their daughters, or a college campus--then a young MC with a big dick, who always has creeper options available to them, must grind away to get with the major female love interests, etc. So every game has voyeurism, groping, sleep sex(i.e., rape), and so forth, even when it really is jarring or makes no sense for a character who purportedly cares about the people in their life and isn't a narcissistic psychopath obsessed with manipulating women into sleeping with him. At this point there almost needs to be a tag:
Erotic Megalomania to cover this genre of "MC seeks to sexually dominate every woman in the game world, including all blood relatives". Hey, done well, that could still be an appealing genre. But not every game needs to follow this kitchen sink, cookie cutter approach.
In terms of escalation, yeah, normally there might be a brief period of going slow and holding off from full sex, but it's exactly that, brief. IRL if someone is not a teenager and they're doing that, there's likely some manipulation or counter-manipulation going on(i.e., that person is trying to get something out of the person they are effectively blue balling--money, personal favors, commitment, etc.). In the limited context of incest, yes, some brief period of incremental intimacy might make sense. Otherwise the distance from first kiss to vaginal penetration is likely only a date or two(if that).