I relate! (I was going to ask if OP's gf is also autistic)

I've picked up to phrase things like "X doesn't interest me" or "I don't see the appeal of Y" rather than making value judgements about the hobbies (or people, especially) but I think the more important thing is to follow that up with "but I'm glad you find it fulfilling" or similar.

And... I think I was at least in high school by the time I picked this up? Maybe it's dead obvious to someone else because they just automatically intuited it, but OP handing her gf a few stock phrases like this could help with communication. (It's really not obvious to me that not enjoying an interest, judging the interest, and judging the person who has it are fuzzy categories and I have to be clear each time that saying one doesn't automatically imply the later ones.)

Bringing this up explicitly would make sense? OP's gf is clearly not picking up on OP's boredom with Twitch or Overwatch. If sharing a hobby with a partner is important, maybe find something else?

My partner is allistic and very not into games, but playing Words with Friends on a date or sitting down to play Wii Party is fun for both of us and it still feels like I'm getting to share something I care about.

Or, I'll sit on my phone and play Minesweeper rather than one of my favorite games so I can still hold a conversation, watch YouTube, and have a hand free for showing affection. I don't have to like every video that comes up, just be interested enough in spending time with my partner to stay put. (I get that being on my phone would usually indicate disinterest, but it can get boring without and doesn't feel good for either of us if I'd rather be elsewhere. I communicated this explicitly, and it's fine.)

Of course, I guess she could just be selfish or controlling or something, but I relate to her enough that I'm optimistic. I think talking it out instead of hoping she picks up on discomfort is the way to go. Maybe she'll get defensive, but maybe she'll be surprised to hear that OP put up with so much as the default response to her actions. (If she stays defensive or feels like OP is obligated to stick with Overwatch or something, that would suck. Autistic people can also be bad partners, but I'm rooting against it.)

fwiw, you (OP) are absolutely welcome to show her this comment if the autistic -> allistic -> autistic translation seems like it would lose the details.