FFXV among other FF games aren't meant to be sandboxes.  They're usually semi-linear open worlds.  FFXV however does seem to be the most open of all the FF games along with FFXII.

It was the only huge game Playstation had when it first came out. They were going to boast whatever it had like it was the second coming of Christ. You'll notice that the campaign put infasis on the art direction over what the gameplay actually looked like. At the time it was the closest thing to looking like an anime there was, so they got big pictures of what the anime characters looked like and plastered them EVERYWHERE. A little marketing deception that worked wonders if you ask me.

VIII was fairly impressive graphics wise, but you got to remember it's biggest challenge was going against what most would consider the greatest game of all time. Everything had to be bigger and better. But by the time VIII came around every playstation game had an extremely cinematic feel. Resident Evil went so far as to have live action characters. Remember, with all that cinematic feel, they still didn't even have voice acting in 8, while other games at the time did. But the success of 7 and a cash flow unlike Squaresoft had seen or will ever see since allowed them to do that.

Now has FF always went for great looking visuals? Yes. But it was never the forefront of their games until X. I have already previously agreed with that , and it marks the downfall with an uncontrollable airship and room and hallway level designs.

That would explain the lack of airship. Lots of mountains, high altitudes, thin air; completely unfeasible to be flying an airship in those kind of conditions.

It's a fantasy based on reality so the physics engine just wouldn't cope.

As long as there's eventually some form of fast travel I could really care less about an airship.

But airships are in the game.....

They did, shenmue and various jrpgs were the first sandbox games who popuazied the whole thing in the first place. Shenmue has many elements who are more advanced than in gta to this day like talking to people and changing the story telling made in 1999

It's not about having airships in the game. It is about moving at ridiculous speeds through the world. Any game will have trouble with that. That's why usually flying sims skimp out on complex environements.

The system is just not fast enough to render EVERYTHING in that complex and dynamic world at a certain speed. Look at No Man's Sky. They don't even have to load many assets from the disks since it is all calculated and rendered real time. And even though their graphics are not nearly as complex as FFXV, they have pop ins because they have to limit the draw distance.

To retain the look of the game, any airship you travel in would have to be limited to at least the speed of the car, if not slower. That doesn't really sound like fun.

If you step into the airship and suddenly the world becomes a mushy flat mass it would be a complete break of immersion.

They don't need to render in so much at one time.  I'd  gladly tradeoff the draw distance and number of objects and creatures able to appear in a calculated area for a fully controllable airship.