I haven't watched the latest couple seasons, but I've been following the discussion here with interest. Most of us are taught in survival training (even if it's just hunter safety class) that shelter is #1, water is #2, and food is a distant #3. That's because in normal, modern circumstances, survival means staying alive for a few days until help arrives, and most of us could go at least a week without food and be none the worse for wear. So staying warm and hydrated is enough.
In a long-term survival situations that would change, though I guess it depends on the environment and the weather. For most people on Alone, food does become the deciding factor. I think a lot of this is because they start out in the late summer, when starvation is going to become an issue long before exposure. An the other hand, a few strong contestants (Roland from season seven springs to mind) have put a huge amount of time and energy into building an excellent shelter, then had good luck finding food later on. But how many contestants have built amazing shelters then starved out? Roland made it because he took excellent advantage of a unique opportunity. Not many contestants are given the opportunity to shank a musk ox, even if they had the ability and nerve. Food is ultimately the deciding factor.
It was interesting watching Clay Hayes' recaps in season eight. He mentioned several times that one of the primary difficulties with finding food is the inability to relocate to a more game-rich area.