The best way I found to arrive at an MVP it is to set a very aggressive time-based deadline, start executing, and aim to release something early to only a few users. Then rinse and repeat with another intermediate milestone. It then becomes necessary to throw out stuff that does not fit, and also even a very early-stage intermediate milestone is the best way to get feedback (esp on onboarding, UX and pricing). Trying to come up with MVP on paper - I've found that whatever you define still comes out bloated.