I think you mentioned a keyword you're ignoring here: product. This enshittification happens in a commercial environment. Good marketing does not require a commercial product.

Doesn't have to be. Marketing also includes a website, that you as a user need to consciously visit to see, which I would definitely consider consensual.

Commercials like billboards are a different story, those definitely suck

good marketing does not require maximizing it, I think. I see where you're coming from though, any effort spent on marketing could have been spent to create a better product. Having the perfect product is useless when nobody knows about it, though, so as always there is a balance to achieve.