Those are all fair points. I was just speaking about incentives for a new iOS developer today. They might see the option to disable IDFA in addition to Apple's lowering of it's commission as a nudge towards creating a paid app over an ad-supported app in terms of choosing a business model.

I'm sure ad-supported apps are still going to exist, but the pros are a bit muddier now. The perceived devaluation of ads caused by removing IDFA, compounded by the lower Apple tax, are probably going to decrease the number of free apps in the App Store.