One, Discord is still primarily used by underage people.
Two, most Discord guilds are not public, this was a case of malicious bots. If you install an app on your phone, is your expectation automatically that it will skirt all App Store rules and dump the contents of your phone on the internet? I hate people that obsessively archive everything, but even I can see the case for IRC being expected to be public. Especially without SSL enforcement on a channel. Discord does not work like that at all. You are advocating for a treasure trove for the likes of Kiwifarms. (Which is exactly how dis.cool ended up being used, as a stalking tool)
Three, the people who say “every litte piece of info on the internet becomes part of the public record, be careful” are also the ones doing the archiving. Nobody else cares enough. Stop doing it. Not everything is worth preserving only because you are a data hoarder. I’m happy you think you’re building the library of alexandria, just make sure it’s not built out of piles of shit and PII.
If it was technically feasible to permanently record every public place outside the internet and make the recordings available to everyone, would you be in favor of that too? Just because the internet makes that technically feasible doesn't mean it's a good idea.