I would agree with you if YouTube had started as a platform that from the beginning publicly promoted videos that were advertiser-friendly, but that's not what they did. For years, their algorithms were tailored only to show users the content that they liked, regardless of advertiser status. They had the goofiest, weirdest stuff perfectly suited to my weird personality. They showed lectures and political discussions that I liked discussing.

Then they made the algorithm changes. Instead of showing me videos I like, they suggest videos they like. Those videos often clash with my values or beliefs, but because they are mainstream, they get pushed anyway ad nauseum.

The change of state in the algorithm could be considered suppression. Another way of looking at it would be just the viewer counts of certain categories of videos has plummeted. Alt-right speakers and lecturers, flat-earthers, trump supporters, racial identitarians, and so on have seen a massive drop in viewers. Right or wrong, that algorithmic change that led to a drop in viewers is a form of suppression.

I want to emphasize that suppression isn't always wrong. A massive site like YouTube has to monitor for violent social contagion and contain that. But I don't think they should then use their suppression as an example of free expression, because it's not.

Edit: also to be absolutely clear here, the definition of "suppression" I'm using is the intentional attempt by YouTube to reduce the viewership and engagement in something.