Great point. I agree to your thoughts on what an MVP should be. And that’s what it is usually — a chance to learn something from feedback received from users. Absolutely.
What often happens though is that some flows cannot be executed perfectly as a designer envisions. It faces ramifications due to engineering constraints, timeline etc. Now, the ideal experience is not shipped, so how do we get it out? Which is what maintaining a UX Debt sheet helps with. To make sure we get back to it at some point and a way to improve it over time as you mentioned.
But yes, it is very hard to get this moving fast.