I don’t think the idea was mature enough. Yes it did try to innovate and do new things but it also was trying very hard to be familiar to an audience that was never going to embrace change while not changing enough for a new audience to develop around it. I would compare it to the Dvorak keyboard, a device that offered only marginal improved efficiency and use while requiring the user to completely relearn from the ground up and have to fight muscle memory for those who used the popular medium it meant to replace. And in the end, most people said it wasn’t worth it.
I was initially intrigued by having buttons on the bottom of the controller, where your fingers naturally would be thus freeing your thumbs to stay on the pad/sticks. And imagine my frustration to realize those rear buttons are just extensions of triggers already on top. Huge missed opportunity imo that a redesign could have given dedicated buttons on the back of the controller to each finger and expand the possibilities for input combos a player can perform.
TL;DR I think the controller was a valiant effort to innovate but didn’t go far enough or do anything sell enough to stick.
On the steamdeck maybe, on the steam controller they are only r1/l1 buttons, I tried many times to change them and the software can’t different them