Encryption key handling is horrible. It makes Matrix a terrible choice for non-technical users.
As a replacement for IRC, it’s fine. Bridging is limited to a small handful of platforms, or a limited set of fairly technical users with access to money to run cloud services and the willingness to take on maintenance of a hodgepodge of software services and the corresponding network security risks. I’d argue that this part was poorly thought out. It puts the core value features out of reach of the majority of the population.
It would have been better to focus on a client-side bridging design. Or, something more accessible. And the fucking horrible encryption design, oy.