IRC is for people who participate in the internet. For them it isn't hard to host their own website or just use any of the innumberable image/video/whatever hosts and paste a link. Discord is for tech ignorant people who consume things pushed to them by companies over the internet.

Bundling up everything into a centralized, proprietary package will go bad for the consumers eventually. But for now they'll trade away their freedom for convenience and enjoy it.

I don't have anything particularly negative to say about the competition, but if you're looking for a completely free and open infrastructure to build on, I don't think anything (besides IRC, but IRC has it's own problems) comes close to Matrix at the moment. I'm very impressed with the project so far. That said, with a reference server implementation in Python, and few native desktop applications available, there is plenty of work to do.

Edit: Matrix already works great as an IRC bouncer for networks which have been bridged.