This is a good post, I feel the same way about the startup I am currently building. I've followed a similar path - built out a very detailed requirements roadmap to keep me on track and there are features on that roadmap that in the past would definitely be "We add that once we have initial traction"

But I also have ideas for ways of pivoting if the full build struggles.

I think MVP is an outmoded idea for a lot of new startups. Unless you truly have some kind of revolutionary tech (like OpenAI) or idea that nobody else has, you have to differentiate on other things like execution and cost.