I don't think AUR is a feature, but more of a hazard indicator. If the distributor isn't packaging so many important things that most users have to turn to external services regularly, they're lying down on the job.
I think you misunderstand the typical use case for the AUR. It's generally used to install fairly niche software that might fly under the radar of distro maintainers. For example, I have CoreCtrl, a utility for managing AMD GPUs, on my install via the AUR. I'm not aware of any distro that packages it currently because it's just too niche of a use case right now for maintainers to pay it any mind.
I think initially it was because the distro repositories were fairly small, agree now it is often a lot of niche stuff now which is one reason people who don’t use the AUR don’t really miss it either.
That package is in Fedora and Debian testing/Sid and the next Ubuntu. There is also an Ubuntu ppa for the and it’s on the opensuse build service.
I guess I was baffled when FVWM of all things was an AUR package. To me, that's something that's been available in the mainstream package set on almost any full-sized x86/x86-64 distribution made in the last 25 years. I suppose it's not popular these days, but you sort of expect it to materialize because it was checked into auto-build processes in the late Clinton administration and never removed.
Yeah if the AUR can stop me from having to compile even just one package from instructions on a github page (like with corectrl, which I also use lol), then it's enough for me to keep using arch. AUR still means you gotta compile sometimes, but it's so much less of a hassle to just search the AUR and hit go then to mess around compiling something manually.
Well that would apply to any distro I've used.. they're all going to have things that aren't in the main repos. It's a feature for Arch in that on nearly every other distro it's probably going to be more of a pain to install them.