For those who are paranoid about this - some of you have a Facebook account, and half of you have a Google-filled smartphone. Privacy is important, but IMO there should be a balance between convenience and privacy - unless you actually do stuff that requires the utmost privacy or you need to stay fully anonymous everywhere as much as possible.
Division of identity - that is, having unique profiles/identities for different types of things you do on the web, using alias emails and anonymous email for certain things etc. - is a more viable strategy than trying to be 100% anonymous on the web.
Commercial social media that is free does and will track your activity on the site, whether for personalized ads or for algorithm purposes. Lemmy and Mastodon don't because they're FOSS, and don't run on ads (99.9% of the time).
If 4chan made Trump win in 2016, Twitter might make Trump win in 2024. Which is a scary thought. Just imagine the level of control one rich man can have over the information highway, Twitter, one of the biggest social media sites in the world, used still by many politicians, journalists and reporters on both sides. It's happening.