Many people use Adblock to begin with, and those that don’t will only have to watch 5 seconds before they skip. Most of the money from monetization comes from clicks rather than advertisements as you have to actually sit and watch the entire ad for it to count. If someone is offering education for free, does it really hurt if they enable monetization? You have many tutors who will sell their content at high prices. The worst that can happen on youtube is you may have to sit through a 30 second ad. I agree education should be free, but that shouldn’t mean the teacher should get nothing for their hard work and effort.