There is a world where if we had more eng. resources we could have more people than problems and we could take stuff on board as it arrives

I don't think this is a realistic world. The cavitation surface area that spawns new bubbles of unvetted fresh ideas grows as things are added. Adding eng resources to get more done makes it grow faster and I don't think there is ever such a thing as catching up.

tl;dr - deciding what to build (and what it looks like in detail) will always be a critical and fundamental function of product teams.