You’re totally right that this is bad, unacceptable customer service and worth criticizing. Don’t take my next paragraph as an attempt to downplay your problem, because I agree with your justification.
That said: unlike Steam games, your GOG games are not lost when your account gets FUBARed, so long as you backed up the installers. GOG provides that capability; Steam does not. I do back up my GOG installers, just in case I ever get locked out like this. I can’t do that with Steam.
You either have the games or you don't. You can't have it both ways.
With the prices of hard drives these days, anyone that truly cares about this stuff can save up and back up game installers. You don't need a fully fledged NAS server with four drive bays loaded to the brim if all you're going to do is occasionally sync the installers with GOG.
Hard drive prices are around a cent per gigabyte these days. With today's absurd game sizes, that's a $20 "keep it after the cloud service shuts down" surcharge. Not great, but not impossible to overcome either.
Nobody backs up their installers because it's much easier to just rely on cloud providers keeping around your game installers forever. That doesn't mean it can't be done if you actually care.
Yes, I remember how happy I was when GOG was announced, that a digital store with that ethos would exist. It's a shame that it has since become soured like that for me.
That said: unlike Steam games, your GOG games are not lost when your account gets FUBARed, so long as you backed up the installers. GOG provides that capability; Steam does not. I do back up my GOG installers, just in case I ever get locked out like this. I can’t do that with Steam.