I totally agree with the idea of your post. Just wanted to share a sort of funny tidbit about the specific example you chose: I work in fare marketing for airlines, and google flights is actually a bit of a boon for us because it drops you directly into the airline booking engine with pre-filled info.

Before Google Flights we were mostly competing against Expedia/Kayak/etc. Now Google Flights indirectly gives the airlines the top rank again, and we're competing against the OTA's for the secondary spots with ads and SEO. I can also anecdotally attest that Instagram ads work very well for airlines. (Well... worked very well, pre march 2020 and all).

I do agree with your main sentiment though, and the case could totally be made that google flights is doubly screwing over the OTA's now. Just wanted to share some interesting anecdata.