I think this is a deep battle-of-the-approaches topic - whether it's better to "rewrite history" or deal with the different shape of past data. But in the history preserving case the data model doesn't need to be perfect up front, you can approach the data in your application in a way that takes into account the evolution. Eg in Datomic there are practices that support this [1] [2].

Of course you can have dev time scratch environments to play with stuff without to support

[1] https://docs.datomic.com/on-prem/best-practices.html?search=...

[2] https://docs.datomic.com/on-prem/best-practices.html?search=...