Most teams are silo'd like it or not. A backend guy or two, a frontend guy or two, layers of management, product, qa, ops people.
If I'm a backend person, I'll talk to the backend guy person if we messed up. If the frontend guys are lamenting among themselves, I find myself not really caring and time being wasted.
There's zero reason that teamwide changes can't be proposed for discussion via email or slack.
It doesn't take domain knowledge to take responsibility for improvement. If your retros are taken up by lamentation maybe you should try to bring more focus.
Lots of companies have teams for back end, front end, ops, etc.
Slack is a good way for things to get lost in the noise or decided by whoever is in the channel at the time. Email doesn't have those problems but discussions can stretch out over days. And people speak more freely when there isn't a written record.
If I'm a backend person, I'll talk to the backend guy person if we messed up. If the frontend guys are lamenting among themselves, I find myself not really caring and time being wasted.
There's zero reason that teamwide changes can't be proposed for discussion via email or slack.