This is the opinion of the uneducated who only see “Raid / M+” “Role” based cast systems and fully ignore the broad scope of an RPG.
To answer your first question about why Era?
Because it offers the most fun PVP you can have next to MoP arena / RBG’s, and the best overall Class balance next to MoP, but with a twist, the class balance is geared toward Leveling, Dungeons, and PVP rather than Raid / Arena.
For me, this is the Apex of “Fun” in respect to PVP because it has so much more depth than any other version. You may think looking from the outside and uneducated perspective that the classes are more basic with less abilities, and this is true on the surface, but once you really start to know the nuance of play and include consumes and Eng items the game is incredibly deep.