The problem is that telecoms are very large, very complex environments, often with poor security controls. Investing in better controls is hard, time-consuming and expensive, and many telecoms are reluctant to do it. That's not great great since telcos are prime targets for nation state hackers as Salt Typhoon shows.
Hacking the lawful intercept systems is very brazen, but even if the hackers didn't don't go as far, and "only" gained control of normal telco stuff like call routing, numbering, billing, etc. it still would have been incredibly dangerous.
This really buries the lede. Telecoms are reluctant to do it because 'doing' it isn't aligned with their priorities.
Why would a telecom risk bankruptcy by investing heavily into a system that their competitors aren't?
If you want a back-door to exist (questionable) then the government either needs to have strong regulatory compliance where poor implementations receive a heavy fine such that telecoms who don't invest into a secure implementation get fined in excess of the investment cost or the government needs to fund the implementation itself.
Now if we're just looking for alternatives for ourselves, cool. But I think the reality is that most normal users do fully lean into the social aspects of Discord. A server like Marvel Rivals has literally millions of users. Players join that discord to socialize with all of those players and build a community around the game.
Going back to something you said earlier:
> Rocket chat is a Slack alternative for people wanting to host a server for a community. It's not a platform, you need to register and login to each server manually.
So the primary thing is that there is no SSO for each server? No centralized auth system? Because everyone I know that uses discord 'found' the discord via some official means of those million person discord's like the official Marvel Rivals one. If the only purpose of the centralized system is not requiring a new login for every server, then a centralized auth system could be implemented by relying on people's other social media accounts. Login with Google/Facebook/Apple etc.