I know that you didn't ask, but my $0.02 is that yes, RasPi's are unreliable. If you use one for as an unattended remote server, it will do you well to include a hardware watchdog that power cycles the device after it hangs. But modern NUCs seem to take MINUTES to boot the BIOS. I had been using various BeagleBones and found them more reliable than RasPi's and faster to boot than the NUCs in the office. But depending…
I've been using RPis and "clones" for internal services for years, and there's hardly any fuzz with them at all. At most a power cycle once a year.
They've endured house losing power multiple times, I've yet to swap SD-card on any of them, they just keep chugging.
But sure, I wouldn't trust my life to one. I just find it odd that people say they're highly unreliable while all of mine just work.