Current Googler here; my solution to staving off complacency has been constantly asking myself if there are other problems I can and will work on - and they don't have to be problems on your team. (Although, I will say that at a certain point, if you're growing, I think your responsibilities should be shifting from solving problems to identifying/prioritizing the problems.)

Every team has a looonnngggggg list of things that they want to do but can't because they don't have the people for it (even if they're not keeping track of it). Frankly there's also a non trivial amount of core language work that's done by people who don't actually work on any of those teams. Getting context can be hard sometimes, but I've done it plenty of times.

Am always happy to chat, my username is pretty obvious from my profile.