This is part of the "Experimental Features". No one is forcing you to enable it. The reason for this animation is that new posts are now nicely pushing the older ones down the new queue instead of having them suddenly jumping down one slot for every new post. In active hours the queue can be refreshed several times in seconds and cause mistakes when a user isn't paying much attention when clicking/taping/voting on the wrong post because they didn't see it getting pushed down.