The only time I see delays like that is when there is something that has to happen like a network data fetch, database lookup, etc. I’ve written a ton of GUIs in javascript/python and they’re all indistinguishable from c++ qt apps I’ve written, basically faster than a human can hope to do another operation short of queuing up keyboard commands via a “keyboard only” interop (say in emacs). When I’ve seen slowness like the latency was always per what I said before data fetch in some format from a slow database/network connection