Let me try to summarize the problem, the way I see it...
- There are a few fantasy archetypes which are truly essential to a traditional fantasy RPG, the Rogue as "a character who gets along with a mix of manual skills, adventuring savvyness, improvisation, quickness, and uncanny luck" being one of them. The Rogue also deals with combat using the same approach, she is not a lightly armor fighter by concept, only by consequence.
- A class-based game is a game which starts off from a few essential archetypes and makes them classes so that players have a mechanical starting point to play such archetype, without having to figure out from a plethora of rule subsystems how to "build" i.e. properly represent such type of character.
- D&D has decided a long time ago (since the start) to be a a class-based game, and it's committed to stay that way. Other systems take a different approach, and maybe a variant D&D also can, but not core D&D.