EDIT:
Nevermind, please ignore the rest of this... I kept trying to run the command multiple times and for some reason now it works??
I closed the command prompt about 3 times.
Then made a new mod folder, then all of a sudden my gradlew commands started working in the old mod folder.
Sorry for bothering you again, for some reason this error came back!
I checked my environment variables to see if JAVA_OPTS somehow came back, but it's not there anymore.
Still deleted.
My setupDecompWorkspace command worked yesterday, and I got a "BUILD SUCCESSFUL" message from it.
I just finished installing Eclipse, opened it, closed it, and then tried running gradlew eclipse.
It gave me the same "Could not find or load java.se.ee" error.
I tried just typing "gradlew" with no commands, and it also gives me the same error.
I understand how frustrating it must be to hear that this error came back after just being fixed, and that it's not being caused by the same thing as last time...
but I hope you have an idea or two on what's causing this.
Oh and also, since it helped last time, here's a screenshot of my current Environment variables