There are a few that do a good job of protecting our messages with end-to-end encryption, but no single one fits all use cases beyond that, so we have to prioritize our needs.

Signal is pretty okayish at meta-data protection (at the application level), but has a single point of failure/monitoring, requires linking a phone number to your account, can't be self-hosted in any useful way, and is (practically speaking) bound to services run by privacy invaders like Google.

Matrix is decentralized, self-hostable, anonymous, and has good multi-device support, but hasn't yet moved certain meta-data into the encrypted channel.

SimpleX makes it relatively easy to avoid revealing a single user ID to multiple contacts (queue IDs are user IDs despite the misleading marketing) and plans to implement multi-hop routing to protect meta-data better than Signal can (is this implemented yet?), but lacks multi-device support, lacks group calls, drops messages if they're not retrieved within 3 weeks, and has an unclear future because it depends on venture capital to operate and to continue development.

I use Matrix because it has the features that I and my contacts expect, and can route around system failures, attacks, and government interference. This means it will still operate even if political and financial landscapes change, so I can count on at least some of my social network remaining intact for a long time to come, rather than having to ask everyone to adopt a new messenger again at some point. For my use case, these things are more important than hiding which accounts are talking to each other, so it's a tradeoff that makes sense for me. (Also, Matrix has acknowledged the meta-data problem and indicated that they want to fix it eventually.)

Some people have different use cases, though. Notably, whistleblowers and journalists whose safety depends on hiding who they're talking to should prioritize meta-data protection over things like multi-device support and long-term network resilience, and should avoid linking identifying info like a phone number to their account.