So many takes trying to boil something super complex into a digestible nugget.
Let’s start with a few definitions. First off, everyone who doesn’t literally get paid to play thinks of themselves as “casual”, even if you are farming +20s and working in Mythic Anduin right now or you literally log in to kill the LK 50 times every week. The word had lost all meaning, so don’t use it. E-Sports does not mean “anything competitive”. When you stretch it to include m+ general play, then literally any ranked group activity is an e-sport.
It’s pointless to argue about m+ vs raid for several reasons. They have different skill checks, have different reward structures and distribution arcs, and fill different roles in the game design. Raids get their difficulty reset every season with new fights to learn, while m+ gets easier over the expansion as more players rack of time in each of the dungeons.
Your mythic +15 is meant to be accessible to raiders and “heroic” raiders. It replaces the badge gear, weekly heroic for bonus rolls, etc. with a challenge that’s doable without too much commitment. The difficulty point for the “max rewards” is meant for the benefit of players who don’t necessarily like m+ for what it is, but want to have something they can do outside of raid for power progression.
Mythic+ is extremely accessible. That’s it’s primary drawing power. To go from +10 to +20 only requires that you improve your personal play. Going from heroic to mythic raiding, it might as well be a different game. Being part of a mythic raiding team is like having a job or being on a sports team. There’s practice, forethought, consideration for personnel and scheduling etc., all exacerbated by the draconian lockout/ID system. It’s far less accessible to players not already on a mythic raiding team, like heroic raiders.
It’s complicated. And messy. There’s no denying that m+ has fervent enjoyers the same as raiding does. And for a lot of people, they view and development as a zero sum game. In other words, any development done that is on something they don’t like is development effort lost to them. Nothing will change that, so there’s no point arguing it.
Lastly, and probably the most importantly, GD is a terrible representation of players. It’s the same 30 people talking and catfishing each other with a steady stream of newcomers who lurk and rarely post. Couple with the fact that human beings are hilariously bad at understanding statistics (but especially probability) and you have a medium absolutely ripe with conflict.