You can request google, facebook or yahoo not to track you. This works in Europe, I don't know whether it works in the USA. Ironically, for the settings to be saved on google, you first need to register for a google account, so you give them more data to identify you and need to trust them.
You can also use software to block access to their servers. The most comprehensive solution is this one:
https://pi-hole.net which runs on a small server (e.g. a raspberry pi) for all your home network. That also cuts you from their services, of course.
Even this last drastic measure will not be 100% efficient. If some of your friends use their services, their mail or their pictures can be used to infer quite a lot about your behaviour. For people at risk (e.g. public figures, activists not liked by the USA secret services, anyone susceptible to be the target of intelligence really), that is a problem. For the general public, less so.
The real acute problem, of course, is that the majority of internet use happens on phones today (and not on laptops computers) and about 2 billions people use android phones. Android phones are configured by default to report all what you do to google's servers (unless you have a Chinese model, which reports mainly to China). They listen to you (to recognise "OK, Google"), report your GPS position, upload your mail, contact lists, calendar entries, pictures and files to google's servers, use google's DNS which means every site you connect to is known to google. They have your phone number, credit card and if you use google pay they also have the list of your purchases. If one use a dating application (which I understand to be an almost requirement for people in their 20s...), they also have your romantic activities. Apps on Android use the firebase SDK which, by default report everything to google. They often use additional SDKs to report to additional servers, e.g. facebook.
We don't know yet the extent of the problem, because the technology to process that massive amount of data is still in its infancy. But the risks, even for the lambda citizen in a democratic country, are quite real. The most obvious risk, for example, is identity theft. If one knows so much about you, impersonating you online is comparatively trivial.