A chrome browser on the same device has maps behave almost instantaneously.
I mostly use maps via an app (Apple or Google, they seem to be the same for basic use). Usually if I’m using a map, I’ll be using it in my car for navigation, so Firefox doesn’t even come to mind.
I suspect, on top of the “maybe it is internal apps” thing I mentioned at first, some of the really bad sites are the really interactive ones, I probably just use the app without even thinking of it.
So its a regular drag for me. If I really need to move quick to find something, I'll begrudgingly open chrome.