In the musician world, "build it and they will come" would refer to creating a really great band by practicing in your parents basement, but never playing shows in the real world. You aren't going to grow a fanbase by playing in the basement. But you could be a damn fucking good band playing music that everyone needs to hear. There is a lot of work that takes you out of the basement. 50%. But if the first 50% isn't there no amount of leaving the basement is going land you anywhere.
Musician equivalent might be identifying few notable bands in a given genre and actually understanding which fans spend money, why, where they listen to it, what other music they listen to, how they discover new music, what songs they share with people, etc; never done music R&D, so honestly stretch, in part because I know distribution is way more important than the actual music, but that doesn’t change that ultimately it’s the fans listening to music that matter. The “build it and they will come” would be making full album with music videos before ever letting single fan or peer familiar with fan tastes listen to the music.
https://www.youtube.com/watch?v=2U3w5Blv0Lg
Your starting point actually matters quite a bit. Iterating to success through market research would be nearly impossible if you chose a bad starting point. Unless of course you go back to the drawing board each iteration. But in this case you aren't really testing and iterating, but trying out whole new things each round. I believe that if you are iterating in this way, then you truly don't have "it". You don't have whatever unique experience, product vision, perspective, etc is required to make the new thing that is going to disrupt the market you are trying to enter. You can't just keep trying things and get lucky in this way. At least not where we are in the cycle right now with software.