I’m actually fine with age gap stories. I’m an avid reader and that’s one of my favourite tropes in the books I read. But, to be perfectly clear, I want the MC who is the younger one in the relationship to be older than 20-21 years old and the age gap to be max 20 years, because that’s just my preference. Also, it’s a matter of how the author will portray the relationship and the dynamic between the characters. As long as the characters are two consenting adults who respect each other and the “dominant” in the relationship - because the older character most of the time is depicted as the most “ruling” of the two (I hope you get my point, I don’t know how else to phrase it) - doesn’t abuse the influence they have on their partner, I don’t see the problem.
Side note : Gender doesn’t matter.
Side note 2 : There are hundreds of stories that involve the mob and criminals in general, so to me sometimes it kind of seems like a double standard.