Ah, I think I wouldn't qualify those as YAGNI decisions, more in the premature optimisation direction. YAGNI is preparing for future integrations that might never happen, or preparing for supporting multiple databases, special users, special circumstances. It is always a decision of doing more work now, versus more work later.
The decision to not use a framework or a library is sort of the reverse in that you're making a decision that you can later reverse by reducing the complexity of your own code.
Definitely agree with you that a part of being a very effective development team is owning as little code as possible, by using as many existing solutions as possible.