Yes? You can make transfers without an extra app or extra account that settle relatively "instantly" whether or not the banks have actually reconciled (as TFA alludes it's basically always some sort of credit). And this is true of many countries in the world, too! And many of those countries still use and support checks.

There are a variety of systems in many countries, the key difference with Pix is that it is very modern and relatively mobile-first. There are not many other such systems in the world yet. How easy is it to pay without a phone? Or without internet? I regularly make payments in places where there is nearly zero cell signal.

Pix charges fees, too, to merchants.

Is Pix guaranteed to be supported by every bank? The mandate certainly doesn't seem to require it, but I'll take your word.

I think the reason that people in this thread don't appear to "appreciate just how practical and efficient pix is" is simply because it's not very relevant. Sending and receiving money isn't particularly annoying in the US. Nor is accepting payments (merchant fees aside -- that's a whole different topic that I am sure patio11 has explored). I am sure that if Pix or something like it was widely available in the US, folks would be singing its praise too. But it's not particularly compelling when most people aren't even aware that something is or could be lacking in the current system.