Is it an excuse? Maintaining code costs money, and the previous versions are provided under the license, and you're free to modify it, pull selective patches and maintain them yourself. While It'd be convenient if the license was a promise to develop and maintain features for free in perpetuity, it just isn't.

I run into this in non-company backed open source projects all the time too. Some maintainer gets burned out or non-interested and all they're rewarded is people with pitchforks because they thought there were some sort of obligations to provide free updates and suppport