When discussing transmog farming in World of Warcraft, "best" is of course a relative term. That being said, literally every raid has at least a few interesting items that are worth exploring and collecting.
Yes, you can now solo Legion raids, and they've even updated the Legacy Loot system so that Legion raids use it.
For me, it's Artifacts and all the gameplay that we had around them that stand out as the best expansion-defining feature World of Warcraft has had in quite some time.
World of Warcraft Shadowlands is in its closed Alpha, and people have already seen gameplay from the Bastion and Revendreth zones featuring the Kyrian and Venthyr factions.
We've all had this experience -- you log in to review patch notes, skim-skim-skim and wait, what is this weird new thing?
Blizzard seems to frequently treat World of Warcraft expansions as self-contained stories, where almost all characters who show up are never seen again.
One of the choices you're going to have leveling through World of Warcraft's next expansion, Shadowlands, is deciding which of the game's expansions to go 10 to 50 in.
I've wanted Titan's Grip tanking for World of Warcraft since the talent was introduced (back when it was a talent) during Wrath of the Lich King, to the point where I actually did tank with it, back when you could viably tank as a Arms or Fury Warrior as long as you dipped 10 to 20 points in Protection.
Battle for Azeroth has certainly not been all things to all people.
I really haven't liked my professions for several expansions -- I think the last time I really enjoyed crafting in World of Warcraft was during The Burning Crusade, if only because that was when I made my Lionheart Executioner.