I'm not sure if you are making fun of people who use a variety of media other than print. Many people have disabilities that make reading more difficult, like dyslexia or vision issues that require using audio media.
I use video all the time because I have slight dyslexia and I can absorb material much faster that way (running videos at 2x).
So, I not sure I understand what you are saying...
They're not sources at all. They're mediums. They convey information from other sources.
You have to look at the underlying sources. In YouTube it's whoever uploaded the video. On Wikipedia it's the source that is cited for whatever claim is being made in the article.
Wikipedia is actually very reliable, comparatively. It's vetted by lots of smart people who verify the information. It's actual better than most content from edited, published sources. Most publishers don't have hundreds of staff checking every fact, but Wikipedia does.
And Youtube, PeerTube and the rest are just communication channels. If Stanford posts a video on YouTube, it's probably reliable info.