Most of these platforms definitely push an agenda but I would argue that we (well not you or I but many people) allow the agenda to pushed. Propaganda and misinformation only works if the people believe it and, sadly, the masses are easily led. If they see that "everybody" is talking about a thing then they believe that the thing is important and if a thing is hidden then they believe that thing doesn't exist.

The sad truth, though, is that most people prefer the sweet falsehoods to the better truth and they lap up the lies like its life giving manna from their "loving leaders". This, however, is another topic for another time, I think.