But has an RDBMS ever been a major source of that pain? I can't say I've ever encountered a time when it has. If you need to change the structure, just write a script.
I'm not saying it's completely painless, but nothing is.
Yes, yes, there are sometimes exceptions, one must repeat explicitly despite having already said it (see: "probably") because this is HN.
When I'm designing an app from scratch I often think about the SQL tables first and how I'm going to build them, and it really sharpens my idea of what my program will be.
I don't see how skipping that process would make things easier.
However, perhaps there are tools that NoSQL provides that are handy.
However I've never greenfielded an actually large application.