This change only applies to HVCs (Hangout Video Calls) and not for HOAs (Hangouts on Air).
Here's the official announcement post:
You'll notice that there is a very limited number of Hangout Apps available in the new interface.... i.e. 1) Screenshare - that's it.
You can return to the "Older Version" for now via the 3-dots in the upper right which is also how you'd get to screenshare if you are on a non-mobile device.
Read the inset box in this picture to see what's new/improved with this update... or navigate to the official announcement post for the same list of improvements.
Please don't shoot the messenger!
h/t: +Michael Daniels for the alert.