Rewrites can be really amazing if you incentivize it that way. Its really important to have a solid reason for doing a rewrite though. But if there are good reasons, the problem of 0 (or < x) downtime migrations is an opportunity to do some solid engineering work.

Anecdotally, a lot of rewrites happen for the wrong reasons, usually NIH or churn. The key to a good rewrite is understanding the current system really well, without that its very hard to work with it let alone replace it.