I disagree that it's merely a UX deficiency, but I agree that it's not a protocol deficiency. Yes, indeed you could just use an IRC bouncer: the problem is that many users don't have easy access to such a bouncer. What IRC "needs" is a network of open bouncers that users can subscribe to.

I couldn’t imagine joining a workplace only to be told that I had to maintain a service to participate in essential communication channels.

So you're saying an IRC daemon for corporate use needs a competent administrator, which is true of most daemons in business situations.

Could it just be a donkey image that spins up with the convenient bits in place?

I have a hard time imagining irc heads don’t have a solution dockerized

I had a bouncer (with push notifications!), but I was in the minority.