Your pro-MC argument is exactly why multiclassing leaves a bad taste in most DMs mouths.
I don't see any evidence that this is the view of "most DMs". Some certainly feel as you do, but this thread is also full of DMs who love the current system.
For my part, I'd say @ECMO3 's experience here is an example of the system working as intended. A player who enjoys the system of customization combining subclasses I never would have thought of combining to create a character with clear strengths (AC, effective use of Hypnotic Gaze) and clear weaknesses (no access to 5th or 6th level spells).