I don't think it is just UOR, people want instant fun not sit and be entertained for 20 minutes. Down the street they run shows old enough to buy a drink so fresh and new in theatres is not the norm but Universal really needs to put something in these spaces.
I think the issue are the theme park shows are too cheesy. Sinbad was so dumb it never made me want to watch it. Put in something actually cool and exciting and fresh, it would do well.