I am not sure what it was... Yes this was a good learning trip about the sky... in a lot of my photos... there was either too much sky, not enough for the wrong kind... gotta figure out what the right amount of sky is
Anytime it is as bland and featureless and white as it is here, try to leave it out of your frames as much as you can. If the sky "speaks" - nice cloud formations, deep blue colour, something like that - it can well be included. But a white sky isn't good. So in the case of a very bland sky, it's not a question of "how much" or "how little", it's a case of "better leave it out".
Lafoto nailed it right on the head. The dead looking sky just kills your picture. It does look like there is some blue there. Can you bring it out in Post Processing? Other then that, you need to crop out as much of it as possible.