The problem with mobile is that it doesn’t provide scrolling events as such but more of a start and finish so any scrolling effect only takes place when the user has stopped moving the page so the animation would happen all at once at the end.
This article explains it better than me and offers some scripts to support mobile. It’s not a simple issue and will take a little bit of work but seems to be the best implementation.
I have an old iphone 4 and no web animation is smooth on it. Menus don’t slide they stagger 