You may have been grandfathered in. I was unaware this was in place on discord until I went back to England a few weeks ago and because I was connecting from a new country it pinged discord's security protocols and it asked me to verify, but prior to that i'd been in 18+ channels (and created them in my own server) from when it was just the "I swear I'm over 18 guys, promise, click" method that seems to have been the default for Europe at least until 2020. The funny part is i was shattered and looked it, and I don't look particularly young for my age either anyway, like if i go to a restaurant waiters assume I can drink.
It's funny too because people are both surprised by how lax age rules are while complaining that "things have gotten so bad you can't show anything anymore"... Idk what the US o'r Canada are like but 50 shades is still PG13 and Squid Game is PG16 in France lol. There's a lot you can watch as a teen. I think the only thing I've seen get the 18+ treatment recently is The Boys and... Yeah duh. I'm not even convinced it's one single scene doing it, just that there's so much of everything all the time that it can get overwhelming.
The only times I've really thought the age-gating was inappropriate was seeing educational stuff about taboo topics get age-gated, because it's often really useful info for help and prevention for younger audiences. But again that's usually a US-related problem, as the websites want to cater to mostly American advertisers who feel icky when their products are on videos that talk about sex.
