Without celestials, D&D risks being infantile.

When I was younger I used to think that Planescape was better played with incredibly flawed celestials. The goodly races were arrogant and flawed, and unjustly exiled angels bordered on suicidal while spending eternity in the Outlands or elsewhere.

As I grew older, learning about different cultures - whether of nations or pockets of people in dorm rooms - and their religious/political views, I became more and more curious about the idea of truly virtuous beings. Once I started writing/reading more on D&D's good exemplars, and tried to think what it would be like to be an angelic being, I realized how fascinating such beings would be since they offered a chance to model our own human striving for moral advancement.

What would it be like to love everyone, even your enemies? What would it be to grow up in paradises, yet to feel emphatically the suffering of another? These are beings that represent the best of us, but they are also pre-enlighthenment Siddartha like figures who won't have our understanding of being born into a world of imperfection.

In fact, while celestials shouldn't be perfect, that they strive to do good makes them incredibly interesting aides and antagonists to PCs. If an economic plan by a wizard king calls for short term suffering of the poor but long term betterment of the nation, where do celestials and PCs stand? What lengths will celestials go in the name of free speech or communal harmony?

And as the years go by, do they burn out? Become desperate, frustrated? They are the inner city teachers, social workers, and honest cops of the multiverse - jobs that we can admire them for even as we worry what happens when they stop caring and go rogue.

Really, celestials offer a level of maturity to D&D gaming that 4th edition lacks now that the guardinals are sleeping with fishes. One might hope that gods vs. primordials and demons as "Hulk Smash!" will lead to avenues of mature moral quandary, but I won't be holding my breath.