On the contrary AUR seems to have a lot more binary packages than source packages in my experience. Tons of package also have a "-bin" version (e.g. yay).
Your "unsupported" comment is a bit weird. It's the AUR user community that supports Arch and makes AUR compatible with it. I don't know why somebody would contemplate the other way around. I mean, it's the while philosophy of the AUR.
I've been using it for the past 12 years and I rarely got any issues with it. I think you fear mongering quite a bit. Sure, you get over some abandoned packages from time to time and once in a blue moon you get a dependency that doesn't install properly. When that happen you post a comment on the AUR or flag the package and it's solved in a matter of days most of the time. It's surprising that such a system would work so well, but it does.
You can take a look here: https://fosstorrents.com/