The target user group for Discord actually is children and teens. Look at that UI and how it‘s trying to sell you „swag“.

Then, Discord is not uncomplicated. From „Servers“ not being servers, multiple account onboarding levels, to what happens when Discord believes you are a bot or are using a blacklisted IP.

I don't think I'm active on any "server" that is predominately used by Teens.

I believe you underestimate the average age.