Lyxen
Great Old One
It's usually easier to learn anything by starting with less complex options depending on experience.
It's true, just as it's true that as playing something complex is not necessarily the intent of the game, learning is not necessary, just as one can enjoy something less complex technically without it being called "training" or "learning".
And the other part is that the game not only has a continuous progression complexity, but that complexity is not the same for all classes for example which means that I really don't see the point in trying to define a range. It does not apply uniformly across the game system, and it's totally useless when considering the various styles of playing of the game.