How did yours break?

I'm going to clarify that I never used AUR while on Manjaro, as that's an important distinction that is often a cause for issues. The most notable issues I remember having were that my grub config changed after an update, and my boot entries were removed. I had to boot manually through the grub command line, then manually fix the grub config. The second was a combination of issues that likely stemmed from a single cause, but I didn't care enough to fix it because it was just the last straw. My system went from working perfectly fine one day, to being a laggy disaster the next. Programs took excessively long to open, battery drain rapidly increased, and performance was horrible. Seemed like a really bad memory leak, and rebooting didn't fix it, so I just installed base Arch which I had already prepared a flash drive for anyway. The timing couldn't have been better honestly, it was like a going away present. Other than that, I remember having driver issues multiple times, occasional crashes that (usually) went away after a reboot or update, but not much specific past that. It's been a few years, so I only remember a handful of experiences. I've never had a distro crash more often than Manjaro.

But so far whenever I ask this I just get vague hand-waving.

There are probably going to be bandwagoners who join in to hate on Manjaro, and most of them definitely won't have anything constructive to say, but that happens with everything. Then you have people like me who used it years ago and can only remember a handful of experiences, and some who can't remember anything useful at all, just remembering being frustrated.