To answer the points raised in brief using the Titan example. I cannot teach people that standing in an aoe is going to hurt if they have not learned so by that point. If enough of the party cannot evade the initial landslide/wotl that is not a teaching mechanics issue, it is a cannot perform the basic requirements of the game issue. Just having more of them does not significantly change the difficulty outside of coverage area. This should have been learned in the first dungeon or prior. To an extent beyond that I am willing to attempt to teach the mechanics of a fight that new people may have not been exposed to up to that point. Repeatedly failling that beyond the value I gain out of it (satisfaction of teaching others/bonus rewards/comradery which in a roulette enviornment I don't really derive any/odds of directly easing difficulty of further attempts, again in a roulette enviornment no value.) I will leave.
Yes, as someone who has never had their sub laps since release of 2.0 I will admit that yes I probably spent hours on this stuff when it was new, and yes it isn't worth as much now as it was when it was new, and harder to find more people who want to learn it in like. However I did so with the people I enteract with on a daily or weekly basis that I actually enjoy playing with specifically in that context when it had greater value. Outside of that roulette content has the community value of passing someone else on the street to get to where you are going.
Roulettes are bait, offering rewards for rerunning content the established playerbase (people who have been around for a while to run content with deminished value to them). If there is no value outside of the bait and the bait is unlikely to be rewarded due to repeat failures there is no bait. If said reward was not based on completion but time investment in a reasonable amount for the time input. Then you might actually see an improvement in people sticking around. This may invite another problem though, people messing fights up on purpose or squatting because the reward is guaranteed.
From a community standpoint, being all inclusive and understanding has never been a proven successful model. There are required levels of conformity that one must meet to be successful in a community communication is one of these. To a certain extent it gets taught yes and the larger the size the more permientations can be alotted for accents giving way to languages. As these permientations grow eventually they get to the point they are too large for an individual to reap benefits from being a part of when put into a small scattered sampling from the group as a whole due to inability to effectively communicate. So we make subsects of the community that we can limit the varience therein and by extension care more about, friends, family, neighbors, etc. which hopefully in a working community web the whole thing together by sebsects shared not in common with the individuals that make them up. As long as the community as a whole can sustain itself ie subscriptions justify further game development and operation (which they more then do) and the subsects I am a part of are thriving, ie friends clearing content run specefically for them. I could care less about the rest of you, and by extension may even not like you for hindering, my personal growth, or the growth of my friends, by not aclimating to the community based on what the community decides is adiquate learning time/quality to meet the average. If and when that time/quality allotment becomes to steep for entry to the point the community degrades below sustainability, or even nears it, I will stretch my interests further out. If that expected average for example is currently the ability to clear content for the no or little value there is to an individual outside your subsects in 3 attempts and is sustainable as a community. Then that is what is expected of you as a member of the community, which may or may not be less leanient then what is expected of you within smaller subsects you are a member of.
tldr: If I am not getting anything out of it, currecy, emotional satifaction of some sort, added community value to the extent I can get use out of. I could care less about you one way or the other, until you are a detriment to one of those at which point I don't like you varying on the severity of detriment.