OppositeofDecay

It's more about how much time is spent doing stuff that is not combo related. Like trying not to get clipped by assists or navigating Peacock zoning is footsies. Trying to open up your opponent is transferable to some extent. Avoiding Skullgirls style resets is uncommon even in anime games but I won't say it never happens. I'm equating fundamentals with transferable skill cause the definition is somewhat vague and it's usually about how similar games are anyway. Very basic stuff like positioning or hitconfirming are almost ubiquitous, but you have to decide whether you get enough chances per match to practice them for yourself. Honestly I wouldn't worry about it too much.

I see a lot of new players in +R quick match, so finding players shouldn't be an issue. I think pretty much any game that is not extremely combo heavy will build fundamentals (and even those often do, just a lot slower).