Alright, using the 400 year reuinion, I will try and explain why I do not believe that Fate or any "God of Fate" (or w/e you call it)...
Robo: I have come to think that someone, or something wanted us to see all this. The different events over time, that we have witnessed. It is almost as if some entity wanted to relive its past.
Ayla: Ayla know! When people die, elders say, see whole life pass by!
Frog: 'Tis true that morals do relive their most profound memories before death claimeth them. Yet those memories are often sad ones.
Robo: Think things like, "If only I had done this," or, "I shouldn't have done that..." triggers unpleasent, old memories.
Okay, this part clearly tells us that the Entity is a dying thing. The gates are created and are seen as it's "memories". How does this apply to Fate? It doesn't.
Frog: Lavos playeth an integral role in the fortunes of the Entity...
Magus: .. so who is this Entity?
Robo: It is unknown, whose memories these are. It may be something beyond our comprehenseion. Our journey may come to an end when we finall discover the identify of the Entity. ... ... shall we turn in for the night?
Now, at this second juncture, from what Frog says (and from what we already know about the plot), how the heck does Lavos suffer Fate at all?
The fact of the matter is that it's not just the most accepted because so many people believe it, but because there is so much proof collaborated to support it: THE PLANET IS THE ENTITY.