Developers volunteering to iron out the harder-to-fix bugs, not to mention architectural issues that require careful planning and perhaps cross-subproject cooperation, are few and far between. You will find that, for every such individual, there will be dozens rather itching to implement the next cool feature, and sniffing their nose at this "maintenance crap".
Point in case, there's a certain setup of LDAP-based user authentification that makes Thunderbird (and some other clients) crash with a not-helpful-at-all error message. A different setup exists that does
almost the same, LDAP-wise, but doesn't make anything crash.
The problem is known for over twelve years now. The fact that a solution would require some sit-together of at least
three projects means it won't
ever be closed.
I voiced some dissatisfaction with the fact that a decade-old bug still expresses itself with a SIGSEGV, and suggested to at least catch-and-report the condition gracefully. I was told, in no uncertain terms, that I was free to "fix it myself", because apparently the maintainers couldn't be bothered.
Welcome to the world of Free Software, where things are not really better, just broken in a different way.
https://bugzilla.mozilla.org/show_bug.cgi?id=292127
Over the years, I have encountered quite a handful of these "eternal bugs". If it gets difficult, it falls by the roadside.