Does it matter? The problem is that everyone uses discord for everything. It's not an isolated platform, it's THE platform if you want to have friends.
If you don't access adult stuff, you don't need to verify age. I'm not giving them my ID, I'm not expecting anything to change about my Discord experience.
Ratings aren't legally binding though are they? I bought games older rated than I was, and it's totally up to people's parents what they're allowed to play. Are you suggesting a 15 year old should be allowed to play the 16 rated game but not discuss it?
All of my use is primarily professional and gaming and has no age concerns