Bro I'm gonna be real with you here: You aren't missing out on much, besides I think teen love is a load of bullshit because it's usually not worth your time and energy to think what you could've done when you were still going through that phase in life, you're still basically young and you still have your whole life ahead of you, besides why worry about having girlfriend now since you still the freedom to do whatever you want with your life, now I'm not saying you can't be in a relationship or anything but I feel like there are better things to be concerned about then getting a GF in life.
You do realize not all people in those fandoms fit into that category of stereotypes right?
Even if Touhou & Warhammer 40K have fat, smiley neck-beards they don't make up the majority of the fanbase, as I have stated previously don't let people define who you are, no matter what your interests are. As long as you like something to a healthy degree than it's usually not a problem.
Even though I'm not really into the idea of waifuism myself I don't see anything wrong with being attracted to fictional characters (As long as it's not to a creepy degree), though with that I said feel like I should drop this copypasta here (Even if pisses someone off):
"You people don’t actually want girlfriends. You want a personified coping mechanism to materialize in your room in the shape of a girl and magically fall in love with you and fix all your problems or something idk. The fact that it’s totally devoid from conceivable reality is itself the appeal because you can keep blaming all your problems on this made up unattainable scapegoat instead of addressing the underlying issues and the fact that most of you wouldn’t be able to engage in an intimate relationship or even truly want one in actual reality. It’s kind of like girls who have romcom syndrome but more severe."
That being said however, anyone can still love Touhou for it's characters but the lengths people are willing go to with them and the unhealthy obsession's behind them still disturbs me.