Earlier quoted context omitted.
I won't blame them. Firefox is a huge piece of software, and is updating every month . It's a bit shitty of Mozilla to expect every single distribution (most of which are run by volunteers) to package all their new dependencies and check everything works every single month.
but you can just use Mozilla's official binary packages, which are tested to work with a specific set of libraries, and I think are built with higher optimization levels (O3/pgo) than what distros conservatively do (O2) because of cargo-culting early-2000 gentoo forums (that was the case a few years ago, not 100% sure it is still the case today as I could not find easily the current release flags).
Maintainers also sometimes need to patch software to conform to their distribution's norm. For example, Debian patches it to accept extensions installed with APT.
And I'm glad distribution maintainers always recompile software themselves, it helps making sure:
1. binaries are really made from the open source code (I know, it's not bullet-proof)
2. it's actually humanly possible to actually compile it from source (my pet peeve in this area is Kafka: it's used everywhere, but no one seems to know how to actually fully compile it from sources anymore)