That fully is on the implementation.The issue with that I feel, is that it’s magnitudes easier to justify doing basically anything if you’ve using magic rather compared to the pure basic capabilities of the ‘human’ body (quotes because of fantasy species) and when using magic basically all your checks get consolidated into arcarna because there’s a magical alternative method of doing basically everything it’s so versatile, but martials have all their skills spread across multiple stats
Creating the Magic version of the Champion and the onus would be on the DM. If the Champion-Mage just has a 1d8 force blast that they can blast 1-4 times, crit on a 18 or 19, can doublecast once per rest can access the whole Wizard spell list, that is on the DM for being overly permissive to casters than warriors.
That's the opposite of an issue. That's bias.