Special world events with mount rewards
New world quests
Expansion of the Suramar storyline
Karazhan questline
And apparently something "hidden" out in the world
There is no barrier to mythic dungeons, they are in fact a pushover. If you're not doing them that's your issue.
I've been doing mythics via the group finder since I was 820. I'm still nowhere near 860 now... few people are.
You're just being deliberately stubborn. Pretending there's an issue just so you can complain about it.