The descriptions of dragons in Dragobane harkens back to the old writings in the earliest versions of the game. Big, scaly, tresure loving, cunning, ruthless. That sort of thing. I always think of Smaug when I read the old texts. But the most famous of the dragons in the old lore of Drakar och Demoner is Blatifagus, a decrepit dragon with his tail end chopped off, with a penchant for playing chess. So there is precedent for dragons with more style and substance.
And as has been said earlier in the thread, dragons are not evil per se. Not even demons are evil, really. They have descriptors that are commonly associated with "evil", but "Good vs Evil" is something that Free League wants to step away from in their games, instead leaning towards giving adversaries motives that might be beneficial for the PCs or detrimental to the PCs health. Dragons and demons are creatures of myth and magic and we mortals do not really understand them. What we see as wanton destruction might have a greater purpose, even if we ants are trampled under the dragon's metaphorical boots.
I'd say that for any dragon to be a centerpiece of an adventure, it surely would be best for that dragon to be fleshed out, given some more tangible goals that interface with the adventure and the player characters' goals. And not always evil, just ... unfathomable. Scheming over centuries. Having plans that make no sense to us, that play out over one hundred years.
A dragon might have need of assistance against a demon and thus will lend aid to the PCs, requesting only a favour in return. Or it might be a guardian of an ancient library of magic tomes, which it will only share with those who brings it a new tome for the collection. Or it might be a gold-hungry hoarder squatting in a dwarven city out of spite, longing for the olden times.
It's very much up to the Gamemaster to decide. And for the adventure writers to experiment with, of course.