I'm on Windows and I don't recall the last time I was inconvenienced by a Firefox update. Like... I can't even remember what it actually does. OP must be running it on a potato or something.
I think Firefox works like Chrome does here. Both give me a little notice in the menu that a new version is ready, and Chrome is a little more annoying about it (turns yellow, then red). I need both for work, and I much prefer how Firefox does it.
The only time I've seen that is if I haven't updated in a super long time (e.g. on my Windows partition, which I use like once/year). If I'm using it normally, it installs in the background and I get the new version when I relaunch it. I primarily use macOS (work) and Linux (home), so I guess it's possible my occasional Windows experience is how things normally go, but I think that's a special case for when FF is so out of date that it's unsafe to get without patches.