Like others have said a lot of the *A Feast for Crows * criticism can be put down to people waiting several years for the book only to find that there’s no Jon or Dany in it. I agree with santosvega, for my money AFFC is probably the best book in the series in literary terms.
As for the OPs question my belief is that Martin has had the broad outline of the story mapped out since the beginning, but as he’s written the books the outline has twisted and turned so much that it’s now a very different tale than what he started out with.