I have never actually built a deck on a ledger board for all the reasons you describe. They have been free standing and only attached to the house for lateral support.
As for joist hangers, they may be fine outside for inland, northern use. In sub tropical or seashore locations not so much. When you are building, you should be looking for 40-50 year life spans at the minimum. Maybe that is just an old fashioned idea though in this "fix it and flip it" mindset those TV people sell us.