Movie Theaters effectively have their markets cornered, should they be forced to host your speech even if they don't want to?
Let's say people watched 99% of video on youtube. I guess that's inconvenient if you can't do your thing on youtube, but that's not a lack of free speech, it is a lack of attention.
Free speech doesn't guarantee that if I go shout on a street corner I'll get as much attention as youtube or any other street corner. It has always been that way.
A newspaper doesn't have to publish your op-ed. YouTube doesn't have to host your video. You can make a website for free to get your point across without going through Youtube, so they're not silencing you either. Not in a free speech sense.
You're just not entitled to forcing others to express your speech for you.