You don't see the value of publicity at all? I daresay the untold billions put into advertisement of any and all stripes the world over disagree with you. Plus, Twitch streams are only a step away from word of mouth itself, the race is organized by fans, not by Blizzard.
And I'd understand your position RE challenge if Mythic was the only game in town, but it really isn't. Now sometimes Blizzard does overtune LFR, Normal and/or Heroic and that's bad, but most of the time it is perfectly accessible in a variety of ways. Since Legion the game really hasn't warped to cater to the elites, since they ceaselessly complain about split runs, systems like AP or Legion legendaries, "mandatory" M+ and other stuff Blizzard put in to satisfy most other players. We're very far away from Cata to WoD style where the elites raidlogged and the rest either did the same or were maybe thrown scraps in between the raids that were the only place to get decent rewards.
Plus, I'd rather the devs make the game they want to make, than just go purely business PoV. Pursuing only the dollar is how you end up with Immortal. In reality of course there's almost always a mix of both but still.