However, we do have to respect that for 5e.....the concept of "rulings not rules" is baked right into the core of the system. It is one of the pillars that defines this edition.A properly designed system shouldn't be ambiguous; it should present clear methods to resolve actions, and the designers should be very transparent and clear about WHY the rules are written the way they are, then offer guidance to say "but instead, you could do this other thing" if you don't care for the rules as written; in other words, giving the DM the benefit of your experience in game design, rather than leave them stumbling around in the dark.
The designers very intentionally moved away from 3rd edition legalese into a simpler system where the DM was empowered to make more rulings. I can respect that you don't like that model, but its hard to argue that the edition shouldn't do the very thing it set out to do in its design goals.
Now....there is room for clarity and improvement, as we hope to see in one dnd. The stealth rules are an excellent example, as they are so unclear and confusing....AND so incredibly powerful....that yes we do need the designers to step in and right the ship. But lets be honest that is going to be the exception not the rule. WOTC seems pretty happy with their design overall, and based on their sales numbers and general user reception....its hard to blame them.
Going back to the flight argument, WOTC is not going to add in a complicated fly system into the core book. Its not going to happen, its completely against their design tenants for 5e. At best, you might see an optional rule in the DMG for a few adjustments, or maybe something in a splat book (again as an optional system). But WOTC is not going back to make combat movement significantly more complicated, their core user base doesn't want that. They like that 5e runs faster and easier than 3e did.