I think 3 routes is fine, and the overall expanding branch tree can be mitigated by not making most girls interact as much as they would.
Because if Girl A is on Love Route, when you're doing Girl B's story and Girl A shows up, you have to account for whether her personality in this scene is one of three routes.
Even AAA games have a hard time implementing these things that I think they were impressed by Baldur's Gate for having that much freedom branching.
Even Telltale Games whose primary gimmick is your choices matter has to railroad the choices at points because it would make it harder to build a game as it goes on. Example is Nick in Season 2, he dies early in the game, BUT you can save him, but if you do he just becomes a very minor character that almost does nothing and gets killed off without choice later, because they'd have to account for him existing and not existing in each scene.
Heck, Mass Effect got flak for this because the whole trilogy was marketed as "dude,all your choices throughout the games are gonna build up to the third game". Then ME3 happened.
Its very hard to keep track of varied choices because again, like a tree branch, they branch.