Edit: glib not glibc
The GNU C standard library has binary backwards compatibility going back 20 years. They take great pains to preserve that. Are you thinking of glib instead of glibc? The former is from GNOME, and the latter is not.
glib 2.0 was released in March of 2002, and has preserved ABI compatibility since then.
So not the Linux community then. Outside it.
Do all the new GitHub-driven programmers who exclusively use MacBooks and constantly rev things with the same frequency not exist? Why is this still being presented as a freedesktop-related problem and not a general problem with creators' fickle and fleeting attention, when we have evidence that the category isn't as narrow as the pigeonhole you're trying to put things in?
Sadly, that ship has passed... long ago. When you encounter a random person about "Linux", they will think of the Linux ecosystem, not just the kernel. In other words, your and GP's definition of "Linux" is different, and they are both correct depending on how would you read it.
(And before you go almighty on definitions, the majority of linguists agree to just monitor - or "describe" - the words as normally and plainly used.)
Like you note, this isn't a problem unique to Linux/"free Unixy OSes". In some ways Linux is actually worse than others, consider Gnome/Gtk Updates for example. Or how things like having a library to read a particular image format are quite normal around here; except that library has like half a dozen incompatible but actively used versions and around 1000 released versions. The Linux environment is very volatile and everything constantly changes and breaks. Modern applications bitrot exceptionally fast in Linux, while the community points to "but look this Xchess binary from 1992 still works". That's neat but covers few real use cases. The same community is then bewildered that both people and enterprises opt for distributions which move at a glacial pace and only releases updated software once every five years or so.