Corporations have to know who you are, individually, to best be able to cater content to you and best manipulate you towards engaging with it. There are broad-brush approaches, such as the headline phrasing choises I discussed in my main post on this topic, but those are significantly less effective than the targeted methods which can be algorithmically applied once you are identified as an individual user.
Now, if you're signed in to something? That's an obvious way to track you. That's why places are constantly pushing you to make an account - not only does it inflate their "engagement" metrics just because you've done that, but it allows them to use fine-tuned targeting methods to manipulate you into engaging further. But that's not the only way. Not at all.
Meta tracks you even if you don't have an account with them. How? Using metadata on items downloaded/shared from Facebook, or installing cookies on non-users when they visit a site with a Meta-linked "share" button. You can break this by using Firefox and installing their Facebook Container Extension, which locks down all Meta activity and restricts it to a different container tab so it doesn't have access to tracking anything else. I recommend doing this with all social media, actually - keeping them in their own little boxes, isolated from your other activities, because they use your account sign-in to assign tracking cookies as well. uBlock Origin acts to block both ads and trackers from other sources as well. It's also good practice to use a trusted open-source metadata cleaner like Mat2 to strip identifying EXIF/ITPC/other metadata from all sorts of media formats. Always a good idea when posting things online in almost any circumstance, lest you do something like accidentally give away your home address (some devices incorporate geographic data into the image!), and cuts Meta off at the knees when it comes to embedding information for tracking in them.
Meta is nothing compared to Google, however. The Google ecosystem exists in its entirety to establish a profile on you so that it can target ads and content towards you on its various services, and while that is made far easier for them if you have a Google account? If you own an Android device you're linked in anyways. Every device has its own Advertising ID which tracks usage, location, and activity in order to target you with content. Oh, and to allow the government (if they're willing to pay up) to tell that you visited an abortion clinic. Yeah. This isn't the sole province of Google, either - Apple has their own version on their own platforms. Good news is, you can disable both.
You can go even further, if you'd like. Instead of just using methods to obscure your engagement profile, you can actively falsify it. This is where Privacy Possum comes in. A more-aggressive variant of the now-no-longer-recommended Privacy Badger, instead of trying to actively block engagement-tracking? The Privacy Possum method instead injects garbage data in "answer" to attempts to determine what you're doing - making your profile useless for manipulating your activity because it does not actively reflect it. TrackMeNot generates false search queries to prevent Google and other search engines from developing accurate profiles in the same way. AdNauseaum does the same thing with advertisement-engagement trackers, invisibly "clicking" every ad it blocks to muddy and confuse those systems. (Many of these have been banned from Chrome for the obvious crime of "contempt of business-model".)
Keep in mind, this is a constant arms race. YouTube is in a continual battle with uBlock, finding ways to disable video playback until you "fix" your browser by turning off your protections. Twitter/X just straight-up blocks all access unless you make an account to sign in, generating a method by which you can be directly tracked (and thus manipulated) - and while you can currently use "nitter" to bypass that, this is the second incarnation of that project. The original was taken offline by API changes Musk made to kill it. Expect that these things may not necessarily be continuously available or functional, and be ready to find alternatives when they aren't. These companies' valuations are dependent upon keeping you "tied" to the engagement cycle they depend upon for revenue, so they don't like it when you try to free yourself - they only offer these services so they can sell your data and eyeballs to other companies, and when you stop them from doing so? In their minds, you're a problem to be solved.
Let me know in the comments if you know any other good ways to become a problem. 😉