I think there are 2 different, yet related, ideas in your question:
1) People are attached to brands
2) People consume advertisements interchangeably with content.
For both of these, I believe they are consequences from "too many choices". This article [1] from the American Psychological Association covers it well, "In fact, some researchers find that too much choice can actually lead people to take less positive risks in making selections and to use simplifying strategies in lieu of more considered choices."
I view "brands" as a pretty reliable way to take a mental shortcut to minimize risk. Instead of making a choice "I want to buy a product in X category, let me compare and contrast each individual item to see which one is the best", you can say "I want to buy a product in X category, let me see if there's a brand I trust which sells it". Note: You can replace "buy a product" with "choose a movie" for your Marvel example and the result is pretty much the same.
With respect to the blurring of content and advertisement, there are entire teams of people working hard to make that distinction not only blurry, but also irrelevant from the consumers perspective. I really enjoyed Johann Hari's book "Stolen Focus" [2], where he explains the point of a medium (books vs TV vs twitter vs instagram) is actually more important in how the content is shaped and how your brain process it, than the actual content being pushed over that medium. Warning: it's extremely possible I am absolutely butchering this point, so if you completely disagree with it, take that more as "tom is bad at explaining it" instead of "Hari is peddling garbage ideas". :)
1: https://www.apa.org/monitor/jun04/toomany
2: https://stolenfocusbook.com/