No animation with MissionControl? Why?
I too, have Duet installed and lost Mission Control animations on last update.

I believe it's some lazy "bug fixing" on Duet's team: Duet was running and I got logged out of my Mac

defaults delete com.apple.dock expose-animation-duration


then run Duet and then

defaults read com.apple.dock expose-animation-duration


It's again gets set to zero.

So my solution so far is deleting expose-animation-duration setting and removing Duet from autostart for a time being.