It's not just advertising. It's capitalism in general. If they don't show you ads, they find other ways of monetizing you. Things that aren't in your interest. "Enshittification" per Cory Doctorow.
It's not confined to capitalism, and it's more than a bit fruitless to frame it as such. A strict command economy would still be trying to advance its own interests through identical methods. Instead of "friend post, friend post, click here to buy product, friend post", you get "friend post, friend post, the Rungra People's Pleasure Ground is proud to announce that Supreme Leader has facilitated the construction of a brand-new dolphinarium, friend post".
Yes, capitalism is bad, and command economies are also bad. However, we are talking about capitalism, because we live in it, and we are not talking about command economies, so I'm not sure why you brought them up.
The implication of the conversation is "if only no-capitalism, then this wouldn't be an issue". The fact that this exact same behavior can (and does) readily occur under a command economy - an economic system very antipodal to capitalism, if possibly not quite literally-100%-diametrically-opposed-in-all-possible-regards - casts doubt on the fact that it is directly linked to capitalism in any meaningful way.
It's also a bit strange to say "we are talking about capitalism" when this is your first post in the sub-thread.
Capitalist systems heavily influenced by Objectivist/libertarian/Mises/Chicago “regulating markets more than hyper-minimally is immoral, oh and I conveniently have also proven from first principles that regulating them makes everything worse in all cases” horse-shit are bad.
Free (as in competitive) markets are indeed great, but capitalism is not free markets. It is, in fact, antithetical to them, since what capitalism really is about is a property rights system that allows for unlimited accumulation of capital (hence the name!), which inevitably leads to its aggregation in the hands of a few monopolists who then strangle said free market.
Free markets themselves, though, are a concept far older than capitalism, and are compatible with a broad variety of economic systems, including many forms of socialism and left-wing anarchism - e.g. Proudhon, the granddaddy of modern anarchist thought, was very much anti-capitalist and pro-free-market.
