I've seen it mentioned on here a lot that promotions/career stability inside google are heavily based around launching new products, and maintaining existing ones is kind of a dead end. Seems like the outcome reflects the incentives.

I don't think it's because they're not putting enough effort into it.

Like most large organisation they tend to approximate a small government and they're inherently incapable of using their resources efficiently. Every once and then they will acquire a start-up that works to give new blood to the behemot.