I think if it had better in game stats or a different choice of ability people would appreciate it more. It is _the_ best/most elegant design out of gen 3, you can't argue that with me. Perfect mix of concept, as few lines as needed, and as few colors as needed.
Natural Cure is a great ability, but without a usable switching move it's only sort of okay competitively.
The issue with Altaria mostly lies in that it shares its typing with Dragonite... who is far and away better. Better movepool, better abilities, (especially Multiscale), better offence, general defense, so on. So, Altaria needed something to make it stand out, be it a better ability or more unique typing.
Personally I'd like to see its defensive capabilities upped so that it could be a decent wall. It already has good special defense, but its HP and defense could be higher. This would make Natural Cure all the better, as most people rely on Toxic to take down most walls.