Which routes did you skip and what's missing?
Well i skipped ferns route to help cassie(i think thats her name, the one we meet outside the warehouse?
I also skipped the scientist route, and while i could still acess the slime orb, i couldn't trigger the cutsene that lets me get to the vents.
Oh and the first time i reset, i couldn't get the succubus abilities, had to olay through the whole or translvania, even the graveyard to get to it.
Maybe put a question if you want to have the succubus abilities or not?
And thats all there was....oh correct me if im wrong, in the forest where we meet that bever girl and boy(forget there names.. AGAIN) i think theres some blessing passive we get from the guy at the end of the temple...i think, i didn't get it when i skipped.
Bassicly all the routes where you get a item or an reaction from an item for.
Hopes this helps!