I think it's funny that my original post is interpreted as me wanting Frank to already have fucked Abby. I never said that.
My criticism is about how Frank is portrayed, about how he's kept dumb and horny. I would've loved it if Frank had actually put his foot down and tried to parent Abby instead of constantly giving in, even if that delayed their intimacy even more.
If anything, I don't think we see enough of Frank's side of things. Worse, when we get a choice about his opinions, we are told by other characters that we're lying or wrong. What if, instead of going to a grave to ask for permission, Frank booked a hotel to get away from Abby for a while? He'd take some time to put his thoughts in order and decide on what he actually wants to do. No external pressure, no asking for permission, just Frank, for once, deciding things for himself.
For me, there's a severe lack of exploration about Frank's attraction. I think we can safely say that if Abby never pushed his boundaries, he'd never even think about doing anything intimate with her. If she came home with a boyfriend, he could've felt some kind of jealousy and concern, but he'd get over it.
Instead of this exploration of increasingly seeing Abby as a sexual creature instead of just a daughter, we only ever see Frank giving in. In a way, Abby is corrupting him. Her actions seduce him into acts and situations he wouldn't be in otherwise. This begs the question if Frank is just getting conditioned and will give Abby what she wants because losing her is too much to bear, or if he actually longs for her touch.