Yes obstructed view cabin is a lottery, you can always get some light in in though which is better than inside, some obstructed view cabins do have a view.! When at tendering ports make sure you pull the curtains in the obstructed view cabin early in the morning, the seaman in the tender dropping down outside your cabin will be looking in.
We often book an obstructed view cabin these days, I get claustraphobic in an inside, have done a couple of cruises in inside, a few in obstructed view and a few in ocean view, NEVER a balcony cabin, too pricey for me.
Have a go at the obstructed view cabins..the upgrade fairy might even visit you.!