Isn't this one of the things Apple was upset at Facebook over (including the fact that they went around the App Store) since they don't allow this sort of tracking?

So maybe them building the feature is not the only reason they removed your app?

This is an abuse of market position in one market to expand in another, and has a long term negative effect on the health of the industry if only the large players that own the ecosystem can profit from it.

I don't see anything wrong here. They just got a really frustrating outcome.

Can’t wait to hear the same complaint from authors of period tracker apps, once iOS 13 is released with the built-in period tracker.

Just kidding. But it seems that it’s the same mindset that likes the government replacing, say, private insurers, ISPs and other private enterprise.

As for me, I do not consider giant publicly traded corporations “private” any more than cities or states.

Either you remove it because it's against the TOS, anytime in the 1.5 years that the app existed, or leave it be. Don't 'coincidentally' remove it the same week you release a competing app. That's just nonsense.