I always say it's like picking stocks. The chances that you've found a truly great opportunity on a project at Google that hasn't been found by 5 more qualified people aren't nothing, but they're pretty small.
When you're interviewing you are interviewing for a role but not with a team. So you don't know what you will be working on, and it seemed like when coming in, new hires always seem to get to be put on whatever. I talked to a couple of the managers who wanted to work with me, and it felt like these projects were kind of silly. Talking with people on the inside, it seems like the way to find something useful is to get in, then transfer to a team you want. But why would a qualified person want to go through all this craziness when they can just interview at a different company and meet the people they will work with, and talk about what they are working on? Like a normal job? It seems like Google's process is highly skewed toward "great for Google, shaft the candidate." Which they can do, because everyone wants to work for Google, so why not only hire kool-aid drinkers?
And just to bring up the empire building again, if every great opportunity has so many people wanting it, it tends to lead to toxic behavior and culture due to unhealthy competition.