I'm a Jira user, but you really struck the chord with the performance comparison. ("sub 50ms interactions" is 🥵🥵🥵)
Jira UI loading time is usually the time for a little reflection, maybe a sip of coffee. Sometimes I manage to squeeze in a little stretch, other time I go shopping or pilates.
Looks like that now I will have to leave those things to after work hours :)