Were we to honestly consider how readily magic - lacking any yardstick for realism - could be balanced to, or below, 'realistic'/verisimilitudinous/associated/whatever takes on non-casters, we'd find that it should be a non-issue. Classes could be balanced in spite of demanding verisimilitude, but they aren't. If class imbalances were just, y'know, techncial errors, then you'd expect they'd be all over the map, not very consistently generating a 'gap' between martials and casters.
If the real issue is verisimilitude, then creating the reality-conforming classes, and arbitrarily limiting the casters down to their level should be fine. It never has been. Not once in any discussion I've ever seen. At most, we might get a nostalgic suggestion of restoring old-school limits on casting - forgetting how often they were ignored back in the day, anyway, because they just were never fun for anyone.