You're certainly welcome to that opinion but you're trying to overhaul the core of the 5e system. You don't have to like it but d20 IS D&D.
Agreed. That variation is built into the DnD system. The expertise isn't about the individual roles. It's about the combined roles averaging out over time. It's about the statistical likelihood.
A barbarian with a negative Arcane check can theoretically succeed where a wizard with a high Arcane check can theoretically fail. That's a core part of the system.
