It's about market capture and the resulting lack of choices allowing market holders to maximize profits by degrading product performance. This can occur even when the product has no price.
That's part of enshittification. Step 2 of enshittification is to entice in business buyers with low prices and changes that meet their needs. Step 3 is to cut costs and start price gouging to maximize profits.
You're missing half the point of enshittification. I'm just going to quote Doctorow directly:
"Here is how platforms die: first, they are good to their users; then they abuse their users to make things better for their business customers; finally, they abuse those business customers to claw back all the value for themselves. Then, they die. I call this enshittification, and it is a seemingly inevitable consequence arising from the combination of the ease of changing how a platform allocates value, combined with the nature of a "two-sided market", where a platform sits between buyers and sellers, hold each hostage to the other, raking off an ever-larger share of the value that passes between them."
I think the price being gouged by Google and Facebook enshittification is your time being wasted for their own benefit. Your time and attention is what they sell after all.
One consequence of monopoly capitalism is businesses pursuing growth in revenue more aggressively than growth in user base.
When the market is saturated, all you can do to pursue growth is to increase unit margin. This eventually leads to production of "fictitious capital" as a stand in for real capital (as paper assets cost virtually nothing to produce).
Das Kapital goes into lengthy detail about this process. Specifically, the "how much does it cost to make a coat" chapter gets into it in (exhaustive) detail.
Monopolization becomes inevitable in a capitalist economy since the wealthy are still the ones with power, and they will always seek to increase their wealth by any means necessary.
Even in a heavilly regulated form of capitalism, the wealthy will do everything in their power to slowly strip regulations over a period of time where they think people won't notice and attempt to move public opinion towards the wealthy class's benefit via propaganda.
By talking about the effect (enshittification) instead of the cause (capitalism). One could read your initial comment and conclude that the only problem is enshittification, and not even think about capitalism as the cause, since you didn't mention it.