I knew you would bring up these other "execution requirements" (which aren't actually execution requirements, they're just other physical aspects of the game that you're introducing for the benefit of your argument). None of this justifies FRC difficulty, though. Obviously it would be very difficult if not impossible to take a fighting game with hitconfirming, delaying moves for spacing, and movement, and to then remove those aspects of the game and somehow bandage up the remains to the extent that the game is still just as deep. Instead of manipulating the terminology to your advantage by saying that somehow "difficult FRCs" fall under the same umbrella as "every obviously-fundamental aspect of all fighting games, ever" simply because they can both be described as "execution-intensive," you should try explaining why the "difficult FRC" flavor of "execution" itself is important.
edit: yeah, basically what EternalLurker said was correct. You're pointing to one "flavor" of execution difficulty, an interactive one, and lumping it together with one that isn't interactive in FRCs. I accept that simply making FRCs less difficult would have a potentially adverse effect on the game's depth and/or balance, but you haven't given anyone reason to believe that difficult FRCs are so important that making them easier would make the game worse even if the game were properly rebalanced afterwards (and no, I'm not literally suggesting that GGAC should be modified, I'm just saying that it could reasonably be done).