It’s a difficult concept to understand, and requires a certain amount of faith / belief in order to take seriously enough to work towards. This is true of all spiritual concepts, by the way. And any time something calls on you to believe before you act, people criticize it. Once you get some experience and make some headway, you can understand what it is and why it’s so difficult for the uninitiated mind, but before then you’re operating on hopes and promises.
People who don’t like hopes and promises sure won’t have a high opinion of enlightenment.