It takes 2 to tango. It’s like trying to send an email from a self-hosted email server without following all of Google’s rules/guidelines… which means you won’t be able to send a message to most (sadly). Most folks are either on Matrix.org or a server they host in practice… you alone self-hosting will only help if you only communicate to folks also doing similar… to which if just one user from Matrix.org (or a server they host) joins your chatroom, then literally everything that is being & has been said in that room will now be synced to Matrix.org by its protocol design. With the expense it takes to self-host Matrix for a community, almost all medium-sized communities had to drop it on RAM & storage costs alone which caused most of those users to move to Matrix.org. You can run a single-user host with some efficiency, but most users are not technical enough for this. The only option to use Matrix & keep costs down is to unfederate… at least with Matrix.org (& servers they host), but that now defeats a huge part of the argument those saying Matrix is federated/decentralized.

It isn’t decentralized in clients or servers either. Almost all servers must run Synapse which is resource intensive but actually has the features folks expect as the de facto reference server & Element is the only viable client considering most users will be using Element-exclusive features like threading, polls, etc. where protocol hasn’t done a great job of providing a progressive enhancement approach to its features & so folks on alternative clients straight-up just don’t see / can’t interact with this stuff.

The accessibility to small–medium-sized communities matters if you want a healthy federated/decentralized network …but luckily there are alternatives.