Brazil's government-run payments system has become dominant

As a foreigner that visited Brazil for some weeks, I found the ubiquity of the PIX payment system to be a handicap for tourists visiting the country.

PIX is only for locals as you need to register with a CPF (Brazil ID number which is hard and tedious to get as a tourist). I ran into many scenarios where the only option was to pay with PIX and the staff aren't used to tourists and look at you funny when you explain you can't use PIX.

Also beyond PIX, if you try to book buses, planes, or take out a gym membership, while you're within the country, 99% of the time it's shockingly impossible to pay without a CPF, even by credit and debit card. I've even seen this for paying the laundry machine.

I'm sure the PIX system is great for Brazilians, and it was helpful having a local friend to make payments on my behalf, but Brazil really lives in a bubble where it seems a side-effect of their system is making things actively very hard for visitors to operate within the country.

Sounds similar to China / WeChat situation, from what I've read previously

It's now quite trivial to connect a foreign credit/debit card to Wepay, and it worked flawlessly on a recent trip. (This was very much not the case only a few years ago.)

It might have worked for you but it's still not trivial. There's many hoops to jump through still like random ID verifications, many banks not being supported to be linked, account locks that can only be unblocked by having a WeChat contact vouch for you etc.