You are assuming that the only downside of building a broken product are the development resources you spent in the process. That might be true for a new product, and only if it doesn't cause damage to your customers. For an established product that needs updates, breaking it means losing a lot of the value that was in that product.
This is literally what happens all the time with startup, it's called "pivoting".
What happens when you can pivot with a new fully built product once a month?
Nothing. A month isn't enough to get valid feedback.
I am patiently awaiting the collapse of traditional saas VC