I don't do mobile advertising but this is just incorrect... Most of Google's revenue comes from Search and that has nothing to do with IDFA.
Then how would third parties with no access to first party data compete when there's no more third party data would be something I'm curious for you to explain.
Ok first of all I am not saying that third parties without access to first party data will compete with google's search ad business.
I think after removal of IDFA, smaller ad networks will steal some of big players mobile market share. And mobile advertising will not move to search based advertisement as much as you think. Maybe some revenue will shift there, but I think lose on mobile side will be bigger.
Removing of IDFA should close the gap between big players like Google, Facebook etc vs others.