Everytime that i hear someone complaining about subsysstems i have to wonder if they even know what are they talking about, many stuff that people call sub systems are not that, like kara cancels.
Outside 1 or 2 subsystems on the current games, the majority are natural inclusions that have very logical reasons of why they are present, but of course that requires an understanding on how the fgs work to begin with, so any new player could have a difficult time to gasp them if there is not a comprehensive way to let them know how the fg works, but the majority of the games out there have tools to teach about those subsystems in the 1st place, plus the info about them is fully available out on the internet.
For example the FCAD is not a concept difficult to understand, but, certainly it can be difficult to do consistently, that is something that i would not deny.
You can cancel some moves at the cost of some bar in order to make an attack safe or keep the pressure/combo, the concept is simple in reality, now the execution part, well, blame ono or whoever you want about that, since if we go by the interviews those “execution barriers” are there because “the hardcore players love them” as they seem to believe.
Also, depth come from options, if those options have an impact on the general strategy.
Continuing with the FCAD example, it adds depth because it gives options that add to the strategy, plus you need to manage your resources (super bar) to have access to it, and the decision of using your meter for doing an FCAD also has an impact on what you can and can’t do after that.
Finally, one thing that many people should understand is that not every game or game genre would appeal to everyone, not everyone like racing games, sport games, fps, strategy games, etc. for whatever reason like gameplay for example.
The same happens with fg.
Edit
Also if you believe that other games don’t have a lot of sub systems that are not showed to the players you are very wrong, just look at quake, the amount of shit that you need to know to play competitively about the physics mechanics is big, or racing games, you need to understand well how the car behaves plus a lot of technical stuff that the majority of the games simply never tell you. Yeah, you can say that anyone can drive, but knowing how to drift, and how the car behaves and how to take advantage of that gives the player way better chances to win.
There where more people playing fg on the 90 because by that time arcades were alive, more than anything, the complexity of the games wasn’t really a factor, since even when game became more complex there were still people playing them.