So how come I've seen so many great movies at film festivals that no critic writes about?
(I've seen some great films at film festivals, but I absolutely have had festivals that were a complete bust. So I took exception mainly to your "guaranteed" claim, which you seem to be stepping back from now)
Well then, to put it more bluntly, I once went to a film festival and didn't find anything that I enjoyed thoroughly. So your guarantee is bollocks.