That’s why, in the system I’m proposing for my own campaign, it would only apply to Wizard casters. All others would use the system and in-world explanation found in the PHB.Following up on my own ramble: In D&D, different classes have different spell lists. Some, like the Bard in D&D 3.*, were really light on combat spells. Like, nearly none. (Glitterdust actually counted as an offensive spell for a 3.* Bard. That's how starved they were for damage dealing spells.)
The Zelazny style of magic would tend to blur the lines from one class to another. Suddenly every caster of every stripe is a combat caster.
Not sure if that's a good thing or not. Leaning towards "not" though, since the different spell sets were one of the aspects that defined a class, the advantage you sought or the price you paid for choosing that class. It makes that choice almost meaningless in many ways.