Yes, this is just part of life. Most open-source developers go well beyond the technically-correct "I don't owe you anything" stance and actively try to help their users, which includes adhering to SemVer, and trying to do more work so that the user doesn't have to.

However, you can't rely on this. Many open-source projects fill a niche and become popular when it isn't the intention of the author. This causes a disconnect where the users expect the project to be for them, when the project is really for the author. Mongoid seems to be more in the former category (for the user).

Because some libraries are badly managed, you need to audit all of them.