You are confusing MMORPGs with single-player games (with a side of RTS).
Single player games are meant to make you the stand out character, the hero who profoundly affects the world, because you are the only real person in there.
MMORPGs are supposed to put you in a world with other people, and thus will of course provide an experience like real life, where only the best will rise to the top and the rest will have to work together to achieve anything.
The whole point of a MMORPG is that the challenge is other players, and only by being better than them can you succeed - the opposite of a world where you are guaranteed to succeed, and the opposite of what you described.
Bosses might take hundreds or thousands of players working together to kill
Real MMORPGs don't have bosses - they have other players.
Your actions would be so diluted as to be meaningless.
In any game where you are merely put in the role of the world-changing hero, your actions are meaningless. You aren't really doing anything, the game is letting you do things. Only in games where you must earn that power, where failure is as likely as success, do your actions really mean anything - that is why MMORPGs exist.