> There aren’t 100k Googlers developing on top off GCP services to get their job done on a daily basis.
Doing something on top of GCP rather than the normal way at Google was a huge pain. Borg tutorials and documentation were just far superior, I could get a thing running on borg in an hour from not knowing anything about borg, I spent a week trying to get something running internally on GCP but still couldn't get it right (our team wanted to see if we could run things on GCP so I was tasked with testing it, I couldn't find anyone who knew how to do it so we just gave up after I didn't make any real progress). That was the worst documented thing I've ever worked with. And even worse the internal GCP pages were probably running in california and probably weren't tested from Europe, so the page took like 2 seconds between mouse click and it responded to anything.
That was years ago though and I no longer work there, but at least back then the work to make using GCP internally seamless wasn't done. Maybe it is simpler if you run everything in it and don't need it play well with borg, but there is a reason why it isn't popular internally. And likely you wont find many engineers who left Google who recommend you will use it, since they probably didn't test it and if they did it probably was a bad experience (unless they worked on GCP).