To be fair, Long Max, any ship, no matter the difficulty, can be made hellish if given the wrong loadout.
As it stands, the difficulties would be a fair "average" for how difficult it is to keep the ship flying. Looking at some of the difficulties now are misleading. It's supposed to be a fair baseline for the captain to know whether or not they should try this ship or not.
The same idea of a 'general difficulty' is what the difficulty level is trying to accomplish. An 'easy' ship in the hands of a novice will fare just about the same as a medium or difficult ship, but they'd have something of an easier time of it.
For example; Pyra is a relatively easy ship. Like, all around. Engineering is pretty simple, gunning is pretty simple, piloting is pretty simple. This doesn't mean that you're guaranteed victory, since it's effectively hwacha-bait and you're going to take a lot of pain from any ship with one. It doesn't mean you can rush up on a galleon and can take it on.
What it should mean is that you're going to have an easier time for A) the pilot to fly the ship, B) get to components to repair them, and C) keep a weapon on target to hit the enemy ship. A general idea for how difficult it is to get to components, how difficult it is to maneuver the ship, and how difficult it is to play as a gunner aboard a ship like this.
Guides are always going to be about a thousand times more effective. But for a novice who has just picked up the game, it could be a help to understand what they're getting into.