Well, whatever we want to call it (whether it's a parallel universe or variant time or whatever) it means essentially the same thing - an easy out for future predictions that go wrong.
But let's think probabilities for a minute. Let's say that there are an infinite (or near-infinite) series of worlds where each possibility plays out. It would stand to reason that the vast, vast majority of them wouldn't be anything similar to what we have now. There must be countless worlds where humanity never evolved, for example. The probability of hopping to one that's so close to yours that it's almost indistinguishable would be like... worse than lottery odds by a cosmic magnitude. You might as well shuffle a deck of cards and predict the sequence with perfect accuracy, down to color and suit. That would actually probably be easier.
