Good search is a huge engineering challenge and nowhere-near solved. Google's continued dominance is what makes their ad space valuable.
If I were google, I would keep investing in improving search, and that would obviously include hiring machine learning and AI experts.
flights, photos, maps, shopping, and a dozen other things?
Which one of the examples you have listed can exist without SOTA search?
SOTA = ?
SOTA means "state of the art"
They all can exist without it, and they all benefit from it. I see your aim in singling out shopping, but let’s not pretend that other services don’t provide signal to influencing the outcomes on shopping or flight purchase or whatever.
I meant as in search revenue: something like 90% of revenue is from ad sales or sales around search