Since it's a game and you're meant to have fun, that should be top priority. That said, if feeling like you're not doing well enough makes you have less fun, then that's a problem in itself.

Black Mages have one of the simplest overall rotations as it only uses a handful of skills in a fairly short, repeating order. The tradeoff is, like you say, that moving at all hurts your damage output quite a bit. I'd give Archer/Bard a go to see if you prefer that - it's a much more free job, not only in terms of movement but in that they don't really have a set rotation after their opener. They also have ridiculous burst damage when paired with a dragoon. The BLM in my static had to really rethink his play when he started doing Coil, but in the end it was very satisfying to see his numbers rise. But yeah, having fun - good thing.