> we didn't know enough about our product direction to make any truly informed decisions.

Bingo. Very few programmers are working on projects that they have many years of domain expertise in, so the data models we come up with are always going to be limited to our experience in the here and now. It's one thing to organize highly technical code around things like graph algorithms are combining multiple b-trees in a single operation to lookup data, it's a whole different thing to tackle line-of-business problems where things are not so well defined (even to the in-house domain experts).

Yes, do migrations well to make it easy to fix mistakes. Don't make vague stupid data models to try to avoid making mistakes by being noncommittal.