The UI has been slow for the MAcOS app and Safari for ages.
I remember it becoming slow after an HA update a year or so ago and it has been that way every since.
I do appreciate that this may be out of HA’s control, but it drives me nuts.
I also appreciate I can use another browser. It’s fast in Chrome for example although you have to put up with a very annoying ‘not secure’ banner. However, I don’t like Chrome or Firefox (hope that doesn’t sound unappreciative as I think HA is great).
I do have content blockers off for HA.