Competitors still exist chief, it is not an effective monopoly yet.

Legal monopoly, no, effective, yes. The US government has even sued them to that effect, alleging they have been using anti-competitor and unfair strategies to maintain its monopolistic power. It may not technically / legally yet be a monopoly, but that is not what an effective monopoly is.

Also yes I do feel you are not educated enough on the matter, as your example clearly shows. It is not "oh no, they know I am out of toilet paper" it is more about "they have location tracking, search habits, purchase history, and more, and now they model predictive algorithms on what variables they need to push to influence you in a specific way". They can extrapolate that some advertisement on your route caused you to speak about X, and the online ad Y afterward pushed you to searching the web for Z, which comes up with specific products or messaging they want you seeing. Now imagine all this data at scale with billions of people and billions of dollars of compute to crunch massive amounts of patterns they can use to push you and others.

It doesn't have to only be about purchases either, this same information can be used to get some political message in front of you, as well as misinformation that you may never properly vet the truth of to sway your decision making over tens, hundreds, thousands or more instances of this.

You can hide behind "But I have autonomy!" all you want, if it didn't work for them they wouldn't be doing it. You will never free yourself of it completely, but why not start reducing your data footprint by not letting your TV record your conversations and viewing habits? Every little snip of their web reduces your vulnerability to it, even if only a little.

But yes, I do agree with your last point. Not really part of this conversation though.