The way I see it, the issue with the flying controls isn't the controls themselves, but the lack of context. They're fine while hovering, but terrible for steering when flying forward, since you are forced to use both sticks simultaneously in a really weird way.
Unfortunately, existing mods don't fix this issue. In my humble opinion, they're just as awkward, but now in different ways.
This is a scuffed mod that provides a workaround for the issue.
How it works
The idea is simple: the left stick is for precision movement while hovering, and the right stick is for steering while flying at speed.
Left Stick: Slow Movement Forward / Back / Left / Right
Right Stick: Fast Steering Up / Down / Left / Right
This is achieved by adding left and right turning to the right stick, and... that's it. That's all it does. I told you the mod was scuffed.
Installation / Compatibility
Install normally into ~mods folder or with Vortex.
This mod modifies defaultinput.ini and is therefore incompatible with other mods that do so - namely, other mods that change how flying controls work.