If anyone else was annoyed by the excessive animations in the UI, it should obey your OS settings for reduced motion:

We now better respect reduce motion and animation OS settings across the interface. Several animations and “easter eggs” no longer display based on your system settings. We implemented these fixes after feedback from users that these animations could cause motion sickness and other issues for certain people.

https://www.gimp.org/release-notes/gimp-3.0.html#user-interface

On linux, adding gtk-enable-animations=false to ~/.config/gtk-3.0/settings.ini will disable the animations. (Although I don't know if that is the prefer reduced motion setting per se, or just override for gtk3, Either way, the animations are disabled).