Briar doesn't make sense to me because you're trading a central server for a central service... If tor is down, you can't message. It's the same POF as cellular, which is insane to me.
It's also a specific procol, which can absolutely be blocked. I don't know where this notion that it's impossible to block tor because it was designed to be censorship resistant came from, but you can absolutely stop people from using it.
It's not even that hard and there's nothing end users can do about it if they don't know how to circumvent it...
It can be blocked, but blocking bridges is a constant whack-a-mole (especially now that they have Webtunnel which, while apparently not as robust as some dedicated obfuscation solutions, is still a noticeable improvement). My bigger problem with Briar is that both recipients have to be online to message, or you have to set up a "mailbox".