Yeah they dropped MT awhile ago. I believe they said they were looking for ways to make the engine more moddable, which would definitely be nice after DE which didn't even have Snapmap.
I believe the megatexture system was replaced in Id Tech7/Doom Eternal go I actually just got around to finishing DOOM2016 , Damn, that was fun, I just didnt have the hardware for it back in '16. Gonna tackle Eternal next