[Someone]

I agree with that. However, Microsoft's problem is that the volume of its new products is too low relative to the volume of its established products.

It is a bit like population pyramids; every country has one, but some are signs of (future) population decreases. Microsoft's, according to one viewpoint, looked like it was on track to expand forever and occupy the whole world (oops; mixing metaphors here), but now looks as if it will/already has reached a plateau, or even will/already has started shrinking/collapsing (there are many variations here; I think they still have chances to win big in another field (for example, XBox or .NET seen as 25-year investments may turn out to be huge cash cows) but I doubt whether that 'big' will be big relative to their current size.