The difference between your example and the YouTube case is in how accessible are the alternatives. If the only store close to you bans you, then it can be somewhere between a major inconvenience and practically impossible to go to an alternative.
On the other hand, replacing YouTube as a hosting platform isn't too hard (I think? I don't actually have much experience with this but there are alternatives).
Of course the big issue isn't YouTube the host, it's YouTube the marketing platform - but even here there are alternatives. Host on vimeo, but use other social media more. More Facebook posts. Get an audience via podcasts. I'm not saying it's easy, I'm saying that I'm not at all convinced that YouTube really is a monopoly in the sense where we want to do something about it.
It's very easy to host a video elsewhere than YouTube.
It's very easy to view a video elsewhere than YouTube.
It's difficult to convince other people to view a video elsewhere than YouTube. You'd have to be on YouTube to begin with to reach them. Sure, there are Facebook and Twitter. But if you want to get off those as well (and I do)… good luck.
Youtube is not a chat app, where you have 10 alternatives (whatsapp, viber, wechat, fb, telegram, signal,...), but it's the site where most users search for videos, and if eg. wallmart had such a monopoly as youtube does, if they decide not to sell your products, you're basically fuked.
On the other hand, replacing YouTube as a hosting platform isn't too hard (I think? I don't actually have much experience with this but there are alternatives).
Of course the big issue isn't YouTube the host, it's YouTube the marketing platform - but even here there are alternatives. Host on vimeo, but use other social media more. More Facebook posts. Get an audience via podcasts. I'm not saying it's easy, I'm saying that I'm not at all convinced that YouTube really is a monopoly in the sense where we want to do something about it.