This is impossible without designing everything far too easy for the appropriate compositions. In a game where every single person wins there are no winners.
In an MMORPG, especially as competitive and big one as WoW, there need to be multiple levels of difficulty in order to satisfy the needs of the different audiences.
There is a difference between achieving something actually challenging and pouring yourself a cup of coffee while juggling chainsaws. Having to inflict artificial challenge on yourself is generally the sign of a weak design or playing a game designed for completely different target audiences.
There is always a difference between a task set by someone else and self-inflicted challenge. It is also worth noting that this game is the developers' vision and they are capable of challenging people in ways in which they could not or couldn't even think of.
The developers are also the ones that set the rewards for completing the various tasks in the game. There is prestige that comes with those and that plays quite a big role in theme park MMORPGs. Arguing that the only reward should come from within won't bear fruit. It is the same as saying that anarcho-communism is the best political philosophy. It will simply not work large scale with humans being the way we are.
You seem unusually invested in the cause. You are also representing an awfully extremist mentality that the game should have no innate difficulty. Furthermore, you are often speaking on behalf of people who you're now saying do not even share the same views as you.