The point of mandatory classes isn't about respecting time or being efficient.

It's there to make 100% clear that you can't say "I didn't know" when you do something that was explicitly explained in the online class.

So now if a new middle-manager has an agendaless meeting, nobody shows up and they throw a massive fit - people can point at the class and say "It's company policy, deal with it"

Sure. But there are plenty of ways to achieve the same outcome without wasting 8 hours of time for every employee. And once you scale this across all the aspects of company policy/culture you want push, mandatory training classes become incredibly inefficient.