Going to play Game Designer for a moment here, describing the MMO I'd like to play.
On character creation, you choose your initial role. Your character starts in a tutorial zone made for that role, and you unlock your starting abilities through the course of the tutorial. At the end of the zone, you've unlocked all your abilities and have been introduced to the storyline-- at this point, every bit of content in the game is now open to you. Questing, PvPing and completing dungeons and raids gives you points that you can use to unlock alternate skills and even skills from other roles, eventually allowing you to spec into other roles on the same character; you gain versatility over time, which is desirable, but not direct power. (This is actually close to how The Secret World plays; I was very happy with its character customization system.) There would probably end up being optimal ways to build for certain roles because perfect balance is nigh impossible and minmaxers tend to make a mountain out of a .5% DPS increase, but my hope is that there would be options and not the One True Build for any given roles.
Endgame progression is purely skill based-- the introductory level dungeons are very easy, the hardest ones in the game are difficult. But the only thing that is keeping you from pugging into the hardest raid in the game as soon as you leave the tutorial zone is your own personal skill, not some artificial barrier where you have to grind LFR for a month to get a high enough item level to be accepted into a normal mode group. The rewards for completing content are cosmetic-- unique armor, titles, pets, etc. Questing also has the secondary reward of letting you see the storyline (and if you find this boring, it's optional.)
This basically would create an MMO with no grinding for gear, leaving a game that's played solely for fun-- I'm honestly thinking closer to a MOBA in terms of being able to jump in and play, but with the ability to play in PvE content and quest through storylines in addition to PvP matches. And honestly, at this point, I think I'd prefer it; I'm sick of having to do content I'm not really interested in just to keep my gear at an acceptable level in case I decide I want to jump back in later.