See, calling it an ad tech company is overly reductionist. Even though it is technically true, it obscures the overall picture, rather than clarifying. It is rhetoric. It would be as if you called it a bit shifting company because the most proximal event to it making money is the shifting of some bits. The statement is actually even more misleading, because a bunch of folks are by default opposed to advertising, so the point of the rhetoric is to minimize all the other stuff and maximize the unpleasant part by obscuring it with this reduction.
Yes, ads are the proximal cause of Google's wealth. But Google is a consumer services company that makes money via the inclusion of ads on some of those services. Most Googlers do not work on nor are concerned with ads. They work on the services I mentioned. The work is to make the services better so they will attract more users. It is by delivering great services that Google attracts users. Incidentally, these users also enable Google's money making machine by clicking on or viewing ads sometimes.
(To be clear, I am not claiming that the services are universally great, only that that is the aspiration and the end upon which most Googlers' work is focused.)