I'm very curious about where the slowdown is coming from. Is it mostly JS on the client or Java on the server? When I ran my own Confluence server on a Digital Ocean VM, it was slow but not unbearable. I assumed it was Tomcat's fault* or the fact that I wasn't using a "real" database on the backend (a configuration Atlassian frowns upon).

*Confluence is built on Tomcat. Don't know if this is also true for Jira.

Now that my Confluence server is on Atlassian's cloud, it seems much slower still. So I have to assume it's not client-side JS because that hasn't changed much; there's some kind of resource starvation going on with Atlassian's servers.