A workaround would be to:
- Set graphics settings to the very minimum
- Reduce the screen resolution of the game (It'll look like garbage, but it should bring the graphics requirements down to around Portal 2 levels)
- Wait for the devs to implement a mouse sensitivity option (which really ought to be in the game anyway)
Sadly 3d Unity games tend to not be very well-optimized. There are far more performant ways to implement the mechanics present in this game. Oh well. Props to the devs for the game mechanics.