

That’s how it is unfortunately. The best way to get people on Matrix would be by communities hosting on Matrix and advertising that actively in their Discord guilds. Providing simple instructions to pick a client and sign up. Show people they can customise how they like etc, that will help, people love shiny things. Once you have people signed up and using the platform, then they can figure out the federation by being exposed to it.
I had the same experience, I think the simplest way is to just have servers separated like they are now in Discord, and you can join them and chat in them even if you signed up at a different server.