I agree with most of what you’re saying, and I’m glad that you share the concern about breaking changes.
What I’m not agreeing on is that it’s only a question of having paid people. It’s also, maybe mostly, a question of caring about compatibility and the consequences of breaking changes. For example, the spirit of deprecation is to give a warning about the future plans of the maintainers, in itself it’s not that big a burden - the inconvenience for maintainers is mainly to sometimes defer some changes to the next version.
And for Parse specifically, breaking changes to the Cloud API were not a necessity, it was for “cleaner” code, an interim version keeping compatibility would have been possible and far less painful for migration. It looks more like a “the maintainer doesn’t worry about it” issue than a “it’s too hard to keep compatibility” issue (I could be wrong though).