Those apps just shouldn't exist.

I don't know how "join your users to a botnet" became some kind of legitimized monetization scheme. Ads are bad enough. What's next? "Participate in a DDOS in order to use our app?"

Sometimes it's botnet, sometimes it's just accessing netflix without hitting big IP range bans.

If there are proxy apps that only do the latter sort of work than I'm actually in favor of them existing and being widespread.

It is the same as when javascript was used to mine cryptocurrency before web browsers blocked it, exploiting other users computers for unfair gain.

Exactly. If there is a legitimate use case for sharing your connection it should be a separate apps users intentionally install.

"train our machine to identify traffic lights" or something

What's the definition of a botnet?