Interesting. Did you glance at the latest Google I/O? There are a ton of things on the horizon that will continue to keep Google very relevant and generate money. For one, I'd like to point out Waymo. Autonomous transport seems like a pretty big business. From my perspective, Google has the lead in AI right now and it shows in all the products that they're beginning to push out.
A lot of engineers work on ads teams. I heard it once before, but search is Google's core. Without search, their ad-serving isn't very profitable. Everything else is a moat around it - Gmail, Drive, Calendar, Chrome. Most media companies are built around the advertising model.
I can't say that you're wrong. Enterprise software does generate a lot of revenue and Microsoft does support it fairly well. Microsoft has also had some wins as of late.
A lot of Google's revenue comes from ads, but I wouldn't label it a "single horse". It's really a stable of horses if you're counting YouTube #2 most visited site and the other revenues its generating from it's G Suite, people paying for Drive, cloud services, etc.
I may be blinded by my bias toward Google products, but it's also crazy that I don't use a single Microsoft product at the moment -- I don't boot my old PC with Windows. I don't own an X-Box. I don't own a Surface. I don't use Word or any of the Office software anymore. I don't use Azure or VS Code as my editor as a software engineer. However, I do know a lot of .NET developers.