First off, that's literally how wizards work in D&D. It's unavoidable unless you want to go the full 4e route of having every class with the exact same mechanics, and (fairly or not) the community hated that.
The real question is: do wizards render martials irrelevant? In my experience the answer is emphatically no. I'm running a 16th level campaign right now, and I've seen the wizard cast Magic Missile upcast to 3rd or 4th level, and still do the least damage that round. I've seen her cast Blight, a 4th level spell, and not finish tops in damage. A wizard cannot touch the steady single-target damage of a martial unless they're blowing high-level spells, and even then, a fighter who uses action surge is likely come out on top. And I'm just talking damage here -- when you get into the fighter's ability to stand in the doorway and soak up eight attacks per round, it seems to me fighters are not replaceable by casters, at all. That's a stark contrast to earlier editions where a wizard could be a one-man party at high levels.
