I've found that sometimes its hard to figure out what to test when you are seeking user-centered validation, and then, as a byproduct of having a hard time figuring out what to test, the tendency is to simply put your head down, avoid testing, irrationally fear user feedback, and then focus on pushing to production.

The plan then turns into "I'll test once it's live, once I have actual usage data". But, testing never occurs, and instead, your product team is faced with scope creep. You (or your stakeholders) think that a product is failing because you haven't jammed enough into it already, so go ahead and jam more features into it. Build all the things!

The cycle then repeats until the product is pronounced dead. sometimes on arrival, sometimes many months or years later.

So, the sooner product creators, designers, and developers let go of the fear of testing, the sooner a team can arrive at a product market fit.