Especially egregious when preventing pasting into a password field. Do they want me to have a weak password so that I can manually type it in instead of pasting it from a password manager?
There's an old, but good, set of browser plugins called "don't fuck with paste" that helps a little, at least.
Setting dom.event.clipboardevents.enabled in about:config to false will prevent sites from messing with cut and paste.
In Firefox
Brave actually added a force paste option recently for such cases.