Or, as some OS maintainer once said:
WE DO NOT BREAK USERSPACE! Seriously. How hard is this rule to understand? We particularly don't break user space with TOTAL CRAP.
Well yes, if the out-of-tree driver sticks to public stable APIs it shouldn't be broken. And analogously here, if the software in question stuck to public stable APIs and didn't reach into private internals it shouldn't have broken.
It doesn't matter who's fault it is in some Aristotelean sense, what matters is the user upgraded to YOUR new OS, and now shit don't work.
Raymond Chen and Microsoft got this, years ago. Joel talked about it. You make shit work, even if it's the software being a fuck.