Oh, Keats… we wish we could imagine a speaker who was less like you. Unfortunately for us (and, well, fortunately for you), it turns out that the speaker of this here poem is pretty much a carbon copy of… you. After all, he shares your sense of impending doom, your desire for love and fame and splendor in all forms, and your penchant for being swept up in your own imaginings.
Come to think of it, if you're an egomaniac (which, of course, we would never call you to your face), we couldn't think of a better way to express your feelings than by fashioning your poetic voice into something miraculously similar to your own.
Hey, we're not blaming you. Not one little bit. After all, when you've got an imagination this rich and varied, why would you try to foist it off onto someone else? Even if that someone else were a fictional voice of your own creation, he would only steal light away from the true sun in our sky… you.
So here's to you, Keats. Poet, speaker, and melancholic extraordinaire. We wouldn't know how to contemplate death without you.