The problem is the content being uploaded to these platforms serves a real and meaningful public, community purpose. Reddit has always been a knowledge base for a plethora of different subjects, YouTube has all sorts of content that has historical importance to the internet, as well as a trove of educational content that is unparalleled in size and quality.
I take issue with that, because it's not the company's content, it's just their platform. The content is vastly more important than the platform, but the companies act as if it's theirs. They do everything based off what the community has built on their platforms, it's their true essence and what actually attracts people.
In the specific case of YouTube, I'd say that content is irreplaceable and indispensable. While it's true that it is a privately owned platform and we don't have much of a say on its direction, I truly believe the content is so important that the only viable path forward to prevent its loss, is to take said platform off private hands. I don't believe it'll ever happen, but it is what should happen, as it's literally impossible to back up YouTube, just like it's currently impossible to compete with YouTube.
