1. People are not quitting. Legion so far has been very successful. Your opinion is in the minority.
2. There are more ways to get gear in Legion than there has ever been (including Wrath).
3. The RNG system has not changed since the launch of the game so I don't know what you're going on about.
It sounds like you're just unlucky, but if you can't get gear which is the only aspect of the game you mention as "content," then you are doing something wrong because it takes very minimal effort to do so. If you're complaining that your gear isn't maxed out BiS right now then durr it's not supposed to be.
If the developers handed you all the gear you wanted then you'd be complaining that there was nothing to do in the game.
*Just wanted to add that content "grinds," are not an archaic mechanic. That's how an RPG works: Time Commitent=Rewards. You don't hear people saying "Man when are the developers of Chess going to update their archaic mechanics and enter the new world?"