Have you figured out if it's Google or software engineering as a whole? I think the safer option, if it's available for you, is to change to a different team in a different part of Google.

Google is huge and if, for example, ads is boring to you, try Google Brain or any of their X projects (self driving cars?). That way you have more data points around what's causing you to slack. It's not necessarily the case that when you do find personal alignment that you won't regress to slacking off.