I don't have expertise in many fields, but I do have some in that one as I've stopped two major mergers and acquisitions and had to work with the FTC on several more. No, they're not. They're nothing close to a monopoly.
They're not even close to being the top of the market share for that industry. Disney’s market capitalization stands at around $210 billion, which is larger than Netflix’s $100 billion, but much smaller than
Amazon and
Apple, which each have a presence in the theatrical and streaming vertical, are vastly more valuable at $1.36 trillion and $2.69 trillion apiece. Both Amazon and Apple are in a position to be able to buy into a monopoly share while Disney is not.
And Disney is as diversified as other media companies since they have Parks, Experiences and Products business that generates about half the revenues that its Media and Entertainment Distribution does. Its share of box office also isn't anything close to a monopoly. They stand around 25%. Netflix and Amazon have around 11% each. And as free ad-based streaming is becoming a thing they're facing new competition with a smaller market share than they used to have.
Now could Disney become a monopoly? Sure. But they're definitely not there yet.