They have a pretty huge privacy section in android settings where you can see exactly what data they have on you and how to opt out and/or delete existing data.
When you set up android, it ask you if your want in or out. You can even set up a new android device without a Gmail account and disable all Google services including Gmail and search. I don't belive you can do this with iOS.
All those nice settings (for google and everyone else) are only for the minimum they are required by law. That means anything that they can claim to be "anonymized" is fair game and not visible to you in any way.
One thing I really do appreciate about Google products is that I'm able to fully disable personalization. My Youtube homepage is completely depersonalized, because I went through their privacy settings and switched off everything. I can't say whether or not Google is still secretly tracking me, but my biggest concern is actually that algorithmic recommendations put me in a filter bubble. Google lets me turn off the bubble.
Amazon, by contrast, does not let me depersonalize my recommendations. Neither does Netflix. There was a period of several years where I would periodically go through my Amazon history and manually mark everything as a gift. This worked for a time, but abruptly stopped one day. I assume Amazon decided I'd marked too many things as gifts and my selections should be ignored.
Did you receive any ads in spanish or chinese recently? did you see any political ad to a party you vehemently oppose? All that is still decided by your profile and history. Just with hocus pocus anonymization on the front end.
So google is not that different from netflix and amazon. they just give you a blanket.
FB's stock prices hasn't changed because we haven't seen if this really impacts revenue to FB. We know that banner ads are extremely ineffective. So if FB ads are still more effective than that, they will continue to capture the lion's share of ad revenue.