The iOS app has never been free and that's the way most people use it these days. Desktop computing is a niche.

This may be true, but as someone who picked up Anki as a desktop app back around 2009 it feels a little crazy.

I also can’t imagine making cards on a phone, given how much switching between apps/windows is involved and how poor mobile platforms are at multitasking. It’s difficult to envision it being anything but maddening.

In America perhaps. Android is more popular in other countries, most people I know use Anki for free. The desktop app and sync are useful for editing cards and managing a large collection. Both of those are free too, but for how long?