I don't disagree, but everyone doing M+ and trying to be the best they can is to blame for that. If you don't add extra rewards for completing the harder runs, then there's no point behind doing said harder runs, other than posterity. Even if you incentivize it by cosmetic things or collectibles, it's still going to annoy a part of the playerbase that plays only for collecting said things, making them que and be denied over and over again. This kind of behaviour is built into human nature; just like the slowest and clumsiest kid would be picked for the goalkeeper or wouldn't be picked at all to play ball at the schoolyard, the player with the lowest score and gear is left behind.
The only way to solve the problem you've laid out is to scrap the M+ system, but I think it has proven far more popular to the devs than they expected it to be. I also think it has helped them retain a large number of players that otherwise wouldn't play, who have moved on from raiding. It also decently complements the gameplay of active raiders.
They need to do something comprehensive about the state of the game and gameplay overall. At this point, and I've mentioned that elsewhere, the best course of action would be to move on from the established world of Azeroth and all affiliated areas, introducing new worlds to explore and new things for casuals to attach themselves to. The sense of exploration and discovering new things is what matters to most casuals.
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I didn't mean it from a purely gearing-based reward system. I meant the overall sense of a proper MMORPG setting, with activities that can be done within. The open world of the Shadowlands is all about clicking between FPs, going to Oribos and to the next zone, where everything you do is meaningless one patch into the future.
Making it easy to obtain the things you mentioned, while having to do very little, is also a symptom of the same problem. I think the same way as you do. Giving too much for too little or too little for too much effort are two sides of the same coin.