(I only watch the Olympics, and only casually, so I'm not really sure of the whys and wherefores, so happy to be corrected if anyone knows better) I think it's that they have to keep moving, throughout the routine, so the skill is in not having the time to set themselves up perfectly for a backflip or whatever?
No, it’s the opposite. You can’t just do skill after skill, you need dance elements to break up the routine, give you chance to catch your breath, and also to move along the beam to get in the correct position- you can’t do 3 acrobatic skills in a row from the middle of the beam, you have to move to the end and set it up correctly.
Unfortunately as gymnastics has got more acrobatic the dance side is lost. So it’s evolved into the posturing for several reasons, one is the lack of dance ability-even on floor now many are more like the men in that it’s a series of postures- the other is if you get too fancy with your footwork you risk falling off. So it’s kept as simple as possible.
The dance isn’t sexual at all IMO, and it’s a shame if that’s what you see rather than the skill of moving round on a 4in wide plank. Plus now the average age of gymnasts is closer to mid 20-s, it isn’t little girls any more.