The pi, particularly the pi zero is still useful if you need something that can run normal software but not a full mini pc. One example I've seen is using a Pi zero as a "wireless usb" where you can plug it in to a machine that accepts files over usb, and can now drop files on to it over the network.

Maybe you could do this with a ESP32 but it's easy on linux where you can use all the normal tooling and filesystem drivers.

I have yet to even get started with ESP32, mainly because software-defined radio is my main use case. Once you start getting into absurdly high sampling rates, you start to need a lot of horsepower, and that's where the more powerful SBCs shine.

As an example, one of my Pi 5s takes an Airspy and an RTL, extracts 11 different FM broadcast stations, then encodes each audio stream and sends all of them to an Icecast server. There's processing power for more stations, but there are none I'm interested in among the others I'm streaming. With the current 11, it's using about 75% of CPU resources with no overclock. (Edit: this is a 2GB model, and it's running in roughly 500 MB.)