Another way to think about Dave's situation is that his utility function assigns the same value to all possible futures (i.e. zero) because the one future that would've been assigned a non-zero value turned out to be unrealizable. His real problem is that his utility function has very little structure: it is zero almost everywhere.

I suspect our/my/your utility function is structured in a way that even if broad swaths of possible futures turn out to be unrealizable, the remainder will still contain gradients and local maxima, so there will be some more desirable and some less desirable possibilities.

Of course this is not guaranteed, but most utility functions have gradients and local maxima over most sets. You need a very special utility function and a very special set of realizable futures in order for all futures to be assigned exactly the same value.