I tried to upgrade my workspace to Minecraft 1.15.2, but I didn't have the menu with the generators. So, I restart MCreator and it didn't work. I tried to create a new workspace to see if it was only desactivate, but no. I delete the gradle file into the .mcreator folder, but we can't create a new workspace and change the generator type. i tried to see on the tracker if someone had the same problem, but I didn't fine someone reporting this problem, so I imagine there is only something wrong in my workspace or something I did wrong.
I will give you my workspace as soon as gradle files are finished to be downloaded.