Big corporations that pay big creators millions per production are just normal studios like Disney and Paramount and nowadays Netflix and Prime. YouTube is the competitor to that. No matter how professional you think of your operation, you're not Christopher Nolan or even BBC Earth and neither is anyone else whose primary distribution channel is YouTube.

Good examples of more or less "free" content that fits PeerTube are cited in other comments, though. Conference footage, MIT OCW, archival footage of any kind of live event. Productions where the work is in putting on the event in the first place. Holding the conference, creating a course, putting on some kind of skateboarding competition, whatever it might be. Incidentally filming it and uploading the footage costs next to nothing in comparison, isn't expected to drive revenue compared to the live attendance, and it doesn't make much difference to the viewers if the footage is terrible. Shitty quality Feynman lectures is still watching Feynman lecture. It was really cool, for a recent example, that somebody found and uploaded phone footage of Caitlin Clark's fabled scrimmage against the Iowa men's team from however many years ago. Nobody cares about the quality of the video or who filmed it. Likely nobody subscribed to whatever channel it first ended up on, but how cares? People who wanted to see a rare real world event would still have been able to find it and it cost nothing to the person who pulled out a phone and turned it on while that event was happening.