> the definition of privacy you use is important
Yes, it is. Defining privacy to mean the very opposite of "private" is pure doublethink/newspeak.
> Google having my data
You're not giving your data only to google. You're also giving it to anybody that hacks Google's servers to take their data at any point in the future (and anybody that buys it from the hackers), and any government (or other entity with sufficient power or influence) that orders (legally or illegally) Google to turn over their data, and anybody that Google might sell the data to should they have unfortunate financial troubles. This list will probably grow as the value of data grows and creative new ways to exploit data are discovered.
I commend Google for taking security seriously. You data is probably saver with them than than many business. However, they are still human so they make mistakes. Hacks will happen even with the very best well-funded security teams using impossibly good practices. When governments are involved, it may not even be Google's choice.
You need to remember that data doesn't go away, so the risk of who it may spread to only increases with time.
> other humans
Humans don't need to see your data for it to harm you. Your insurance company doesn't need a human to feed data from Google (or whomever) (possibly blinded through some sort of "rating service"?) through the machine learning and/or "risk assessment" heuristic du jour to raise your rates or deny coverage.
> centralized power
Pretending the world is just[1] - that your data will somehow be limited to only Google - gives Google a lot of power, that will be hard to reclaim. If by some miracle they are able to do better than most people throughout history that acquire power and only use their power for benevolent reasons, the same cannot be said indefinitely into the future.
[1] https://en.wikipedia.org/wiki/Just-world_hypothesis