You seem to miss the point. Do people quit because they can't do 20+? No. Some are content to never even get to 15s let alone 20s. Do people quit because they can't do Mythic raids? No. -They do Heroic and are content to do so. There's a psychology going on, where players want to feel rewarded for their efforts, despite what the effort or stream of content is. There was once a line in the sand and that was guilds and when Blizzard slowly killed off the requirement to be in a guild in order to raid, the skill of the average player declined.
I need to tell you why. Peers. Good players in guilds would teach bad players and those that didn't learn and adapt were benched and left for guilds at their level of play. When this is controlled via content streams such as LFR, Normal, Heroic and Mythic raids, then you'll find that players don't feel the need to be competent at their class and really don't have anyone to look up to and offer them personalized tutoring to become a more solid player and hang with the big kids.
This is the root cause of the problems, players are playing an MMO in a bubble and need little to no interaction with other players at all. There's a give and take in terms of cost versus benefit and Blizzard certainly did weigh the costs and saw the benefit in shattering the more casual guilds in favor of making content more accessible to players who had either little time or care to push toward end game. Few did Sunwell in BC. No one quit because of it. Few did Algalon in Wrath and that wasn't a reason to quit at all. Just like in vanilla with Naxx and even AQ40. Less than half the playerbase even zoned into Naxx during it's cycle.
Content streams now give players options to stay in their lane and some bleed out of it because there is little to no gear disparity between streams. Over time, with persistence even the most casual player can access some pretty decent item levels and happily give the illusion they are a competent player while being sub-par in every aspect of their class; spec, rotation, talents and even addons play a significant role in solid play. -When many players have no idea such things even exist and have no real connection with others in order to refine and master their class, they are left feeling pretty hopeless and are certainly the ones that quit in the end.
So you are totally wrong. Blizzard is totally wrong. I'd honestly say I have more /played than ANY person at Blizzard and can quite honestly say they got it wrong. We all did. There needs to be a slow push back into guild structures and the need for newer players to access the knowledge of their fellow gamer not through wowhead or youtube or twitch, but the way I learned- through my fellow gamers who put in the time and effort to theorycraft and master their class.
Blizzard is so focused on polishing the carrot they forgot about the stick.
THINK. If OP was in a guild would such a post even exist? No. If every raider were guilded or the greater percentage of raiders all guilded instead of PUGing would the game and the general skillset of the average player increase? Thereby making it more fun for all involved? Yes, it would. Think of it as like a poorly trained dog, the dog is frustrated because the owner yells and the owner is frustrated because the dog is poorly trained. Humility goes a LONG way. Blizzard needs to take a humble step back. The drawcard for vanilla was what? Guilds. Great success too. Shows people don't give much of a damn about content, they care more about one of the Ms in the MMO and Blizzard needs a bonk on the head and to roll some heads to get back on track to what a real MMO is about instead of being so fascinated with it's own reflection in the mirror. It's a company run by people and people make mistakes, they also draw forgone conclusions as to what players really want when logging in. It's got nothing to do with pixels. What has kept me going for 18 years with an average of 4 hours per day in game?
-One of the Ms in the MMO. I have a massive friends list and Blizzard would do well to be reminded of what made them love Everquest so much; playing together as a guild every night. Many newer players don't even bother to look to guilds at all, and I don't blame them, there's really no incentive to do so. One problem compounds on another and Blizzard is foolish not to see it plainly. -Or too scared to go back or change the current state of player interaction. PVP is a massive reflection of this; it's dying and what we have left is soft gamers crying about faction hatred saying it's naughty. -That's the bottom of the barrel speaking right there.
One step Blizzard should make RIGHT NOW is guild housing. A guild lodge would do a LOT for the game, as would a 'account' bank- ie a bank that all toons can access. Many players like myself have their own guild simply because it's nice to have a bank that every toon can access. Many are reluctant to leave their guild because of this. Guild housing, account banks AND shared rep/gold/currency across your entire account would be a HUGE draw for the many that have quit. That along with guild housing and guild level progression ie Mythic would be a huge step in the right direction.
So no, if you make things rough, many do actually come together to overcome the difficulties and just about EVERY person who went back to classic or TBC wanted to either feel that again or touch on it because it had been raved about to them in the past; probably the very thing that drew them to Warcraft in the first place.
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Speaking of flawed metrics; Fat Joe CAN still jump. What metric are YOU using? The height? But he can jump, so it's not hard, getting height is.
I like your arrogance in saying the arbitrary you know more than 90% though, it made me laugh out loud. Really.