> I don't have this issue, I can interact with a window just by hovering over it with the mouse pointer

Hm, maybe it's just Firefox that's a bad citizen here, like with the global shortcuts.

Do not blame Firefox, this is actually how MacOS UI works by default: https://apple.stackexchange.com/questions/269622/macos-windo...

I think the other poster has some addon installed and forgot about it.

I don't think I do, I'm a fairly recent convert to macOS. I'm running Big Sur and I can interact with any window the mouse cursor is over. I can scroll any window I'm hovering over, and with a single click can perform an action.

Same. You have to click the window before typing something, but scroll does follow the mouse.

How about button clicks?

No, but I understand the rationale. A button click is an input much like typing. Plus, when I want to give a window focus, I'd rather not look for a non-button to click.

But, having clicks work on hover instead of after focus is fine, and simply has a different set of trade offs.

you have to hold 'option' to click on a button in a window without focus

Not Option, but Command. If you hold down Option and click in another window, the current window hides. You can also hold down Command and drag a window that doesn't have focus.

You can also switch focus to a window without raising it by holding down Control+Option and clicking the window.

At any rate, a lot of these things can be chalked up to different philosophies, I think. Personally, I really don't like focus follows mouse; when I was using FreeBSD and Linux many years ago, I would try it and then end up disabling it after a short while.

It is worth noting that Terminal has a hidden preference for focus-follows-mouse:

    defaults write com.apple.Terminal FocusFollowsMouse -bool true

You can also change that setting, along with those of some other quirky system things, in third-party apps like TinkerTool and Onyx.