What is a non-theistic approach to enlightenment? Does it involve an 'afterlife'? Or some altered ideal state as it's end goal?
For me, these kind of things would define it as religious, even if no specific deity were involved. I tend to consider any such 'supernatural' goals or states to be religious motivations. But what you're referring to may not be 'supernatural', in which case I would agree that what you're talking about is probably not what I'd consider a religious motivation.
In any case, though, I don't think there's anything wrong with religious motivations. If Buddhism is a religion for whatever percentage of people who participate in it, I say all the more to the good.