> but never have I heard about them implementing insecure protocols.

That's because they don't. Google takes security seriously. There's a reason GrapheneOS is only supported on Pixel devices currently as well, because of certain hardware security features.

Nothing you do with Google is private from Google but it's certainly designed to belong only to Google, your data is one of their most important assets. Of course they are going to secure it and prevent others besides themselves from getting or using it.

It's the most common misconception with Google, that they "sell your information." They don't, they never have. They use your info, aggregated with all other Google users, to sell targeting for ads. They don't sell the actual data.