(If you enjoy the last few days' postings, don't worry. Some bonehead will say or do something to merit my commentary soon enough.)
World of Warcraft: Legion makes major changes to the game's mechanics, changes that any player currently playing or returning from a break ought to know and know in-depth. Being properly informed means that you can make the decisions you need to make to maximize your enjoyment of the upcoming expansion. (Yes, including not playing at all.)
This is where the community comes in, specifically the people who take the time to dig deep into the mechanics and see how they work in actual play. I'm embedding one video by Finalboss as an example of this sort of information being made available. Preach Gaming, Belluar Gaming, Fatboss, and others like them are also contributing guides and reviews of what content and mechanics is new.
It's your entertainment time, so I would hope that you respect yourself enough to want to take the time to investigate what is available and discern what--if anything--you want to do with it. Furthermore, I would hope that you respect yourself and your fellow players enough to know what you want to Git Gud at playing. World of Warcraft, especially at endgame, is very much group-focused and team-focused, so being able to play competently will only lead to superior entertainment value for both you and them.
I am grateful to community people like Finalboss and others like him, not all of whom stream or maintain a site or 'blog, for taking the time to dig through all this data and process it into something comprehensible for the rest of us. You guys are the real MVPs.