Don't build high fidelity mocks
When you are building a MVP, don’t go for high fidelity mocks on Figma till you are clear on what you are building. I would say don’t even go for low fidelity mocks on Figma.
Literally just use pen and paper. Shape up by Ryan Singer is an amazing book that you should read. Will help you get clarity on how to build an MVP & how to iterate fast.
When I work with founders, apart from telling them to read Talking to Humans and the Mom Test, how to test their assumptions through an MVP is the first thing we discuss.
Seriously, if you have not read Shape up by Ryan Singer, you should.
Even worse is starting to write code without knowing what you want to build.
As a PM I never let anyone start wireframing till we are clear on the WHAT. Once we are aligned, we do low fidelity wireframes, make sure all stakeholders are aligned and we have kicked off the project with devs, and understand the trade offs, and then only go for high fidelity wireframes that devs can use to write front end code.