> Google had creepy marketing based on private email content (making you worry about what else they are doing with my private email content
As far as I know, email content was never used for ad targeting on any iteration of Workspace/Gsuite/Google Apps for Your Domain/etc. (And it hasn't been used for consumer gmail for many years either.)
Not that the details of how they use a specific information stream are all that important (if they aren't using one it's just because they've got something else better). The fundamental problem is that their interests are fairly heavily misaligned with mine. They want to make money by effectively mining my information and I don't like that and find it creepy.
Because they've made public statements to this effect, including in the privacy policy.
Why trust those statements? Because lying would be a very bad idea. The lies would be revealed very quickly (e.g. via whistleblowers). The outcome would be expensive civil lawsuits, probably billions in fines, and a loss of trust in their $20 billion / year cloud business.
As far as I know, email content was never used for ad targeting on any iteration of Workspace/Gsuite/Google Apps for Your Domain/etc. (And it hasn't been used for consumer gmail for many years either.)