Yes, JIRA Cloud is unusably slow and their "nextgen" rewrite only compounds problems by adding workflows no one asked for and by removing workflows everyone depends on.
Properly configured on-premise installations are usually quite fast.
> I think it makes a lot of round-trip requests.
It does, and that's the main issue
Edit: I did have the bad luck to discover it performs pretty horribly if you’re on a high-latency connection to the office. I think it makes a lot of round-trip requests.