While I agree, I must say that GBA emulation is a bad example here.

It’s one of the few things you can "easily" sideload on an iPhone without jailbreaking using AltStore (the emulator is named Delta, btw and it is excellent).

I will not say that AltStore is really practical to use but GBA and GameCube emulators are basically the only things you can sideload without a lot of pain (along with UTM, a virtual machine runner.