There’s a small amount of truth to those sentiments. You can only pivot an existing product so much. Sometimes, to deliver an entirely new kind of value, you have to do it in a different context. You won’t be able to iterate your way into it.
An incredible benefit of designing your marketing page and your NUX early is that right away, you can start getting feedback from people.
These questions ought to be considered almost immediately after you have your initial North Star, and I can think of no better tactic to do so than the following: design the marketing page and design the new user experience.