I agree with part of your perspective, but you also have an implicit element of suggesting that a person's behavior outside of a relationship should be equivalent to their behavior inside of a relationship, which is nonsense. When you enter a relationship, you are agreeing to a partnership to some extent. It's extremely reasonable to think that playing video games for "several hours a day" is probably acting selfishly when you have a partnership to consider.

What is more measured is to suggest that each person should have some free time for their activities. Not that one person gets several hours of video game time every day because don't change me!. That person sucks to be in a relationship with. Fuck that guy.

And yes, the same does in fact apply to a partner reading all day to the negligence of the relationship. "Hey, do you mind to put your book down for a bit so we can hang out?" Not at all an insane thing to say.

Women can joke about making their man unfollow women on socials and stuff but if a man made his girl unfollow all her male friends that would be weird.

It's actually weird both ways. You are arguing that a loud and marginal state is a default state. It gives the impression that you think posed social media life is the actual life, and this stuff out here in the world is secondary.

In conclusion, it’s just super weird to get into a relationship with someone knowing their daily habits, and then try to completely change them.

That would be weird, but it is also not that common and the vast majority of people are exactly against it as you are. The majority of your argument seems to either conflate "adapting from single life to partnership" to "completely changing" or else to hold up marginal weird behavior as being the norm when it isn't.