Vikingkingq
Adventurer
Nope I'm not describing a classless system. Rogues would still have many other features that a fighter who took sneak attack as their specialty would not have.
If any class can take the main class mechanics of any other class without reference to Specialties, its a classless system, because there are no boundaries between classes.
If what you're talking about is Specialties, I'm fine with that, because they're grounded in past training. An Acolyte Fighter has studied "the rites, rituals, and doctrines of their order....under experienced priests," Magic Users likewise might be "clerics devoted to the god of magic or wizards who apprenticed under a master for many long years," or a magical college dropout.
What I don't like is the idea that any player can use class mechanics of another class without representing some form of training to explain how they gained this specialized ability.