Looks great from the demo https://avodemo.herokuapp.com/users/sign_in

My only suggestion would be to perhaps try out a beefer instance for heroku or perhaps it is http/1.1 limitation of heroku and a switching to one of the disruptors like render.com would help performance?

It also may completely be because I am in the UK. Clicking around just feels slow 700-800ms+ response times, assuming its hosted in US.

Also another quick fix might be sending the request on mouse down. I know unpoly (side competitor to Hotwire) does this https://unpoly.com/a-up-instant