And do you think that people would still do the same amount of world quests, islands and all that other shitty content as they do now if all they offered was a transmog set or a title? This is the argument, Blizzard thinks that these systems having such high engagement is because they are fun, not because they are a stepping stone into better content.
And just to be clear, I don't mind islands and warfronts and all that stuff existing, what I mind is their reward structures. If they existed in a capacity that made them optional for a high end raider/M+ runner, then it wouldn't even be an issue.