I think problem with Bary-centre is that, iirc (played PES 2014 very little long ago during the year it went out) it was always active. However, PES 2021 has a magic button that let's you switch between using body feints or using the RS to do tricks with the ball. And that's precisely what you want to do, let people use or not your system cause maybe some adapt to it, some others don't, and also it might be a very situational system. Besides you want to have a stick have several uses.
There's s also something else IMHO about Football games and something about FIFA I used to like that is how intuitive is your control mapping. FIFA used to assign RT to sprinting, and LT to slow dribbling, alongside with LB aswell for certain dribblins in certain entries. This allowed for a enormous array of variables that could be used in a match while maintaining certain coherence and intuitiveness with other time of games, apparently not connected to football games, but more connected than what you may think. Racing games. In racing games, as in cars, the right trigger is the gas pedal and the left one is the brake. It's like that irl. So using that mapping for Sprinting/stopping the character, is gonna be much more logical than using RB, for example, like in PES. To the point I ended up mapping sprinting in PES to RT simply because is more natural for me, besides it allows me to keep a more relaxed grip on the pad. Another advantage is that if you want to allow to have different rythms of sprinting, like sprinting slower to control the ball easier when you get to catch it, you can make it with a trigger, but not with a button, and same for stopping a player, very similar, precisely, to how a car works, gassing too suddenly or braking too suddenly doesn't tend to be a good idea unless you know what you're doing, and exactly for the same reason in both cases. Inertias. Is easier to handle inertias if you can control them with a trigger (besides smooth movements in the sticks).
At the same time, you can hold both triggers to enter a different kind of dribbling state and you would have even both shoulder buttons for making different dribblings. Due to left shoulder button being the one to make smooth aerial pasess or shoots that require finesse, it could be used to alter how a player handles a ball, being a modifier to use more smooth movements on the ball, and you could use RB to use manual commands AND... trigger that marvelous Bary-centre system whenever you want, something that would feel logical since Bary-centre was quite a manual system. That way you have 4 buttons that can modify how you treat the ball or how you use your body, giving the possibility of a wider array of animations controlled all by player, and that translates in something good... More complexity in dribbling and therefore, a higher skill ceiling while maintaining certain logical and intuitive control scheme. Just to sum it up.
Right trigger: Sprinting, power shooting.
Left trigger: Stopping, doing sharp turns and stops with the ball, suddenly stopping the ball, precisssion shoots.
Left shoulder button:aerial long pass, lob, wall pass, precise handling (things like jumping with the ball over a sliding tackle, etc.).
Right shoulder: manual passing, Bary-centre system.
Right stick: moving the ball towards the different sides (the way of doing it depending on the modifier) pressing the stick to make different hat tricks.
Why they didn't make it? Cause they are LAZY. And because they were simply too busy figuring out how to make the engine work.
