It will also be really hard to offer the same quality and reliability that YouTube offers, without taking a larger cut than the 45% that YouTube takes.
Why do you assume so? Peertube instances have been pretty good for me so far. I rarely stumble upon unavailable videos nowadays. Still a little salty that they implemented their own protocol making webtorrents unavailable --> no headless seeds.
many of the Fediverse users are anti-adds and will run an add-blocker and maybe even sponsor-blocker.
Are you assuming monetisation = ads?