Warhammer Fantasy tabletop is kind of my default. It fits, mostly, but I'm also really familiar with it. If you tack on some notions from DBA to account for the scale of units it works for me.
Yeah, WHFB more or less displays this. In the base assumption of D&D, having PC level ability scores is super rare. And even having elite NPC scores is rare. And it isn't that strong genetically.
So Noble families, high and low, of elite or PC stats would be rare outside of divine intervention. At best, you'd need an organization scouring the nation for special individuals to train into mages and paladins. Default D&D looks like Bretonnia or the Old Empire. You won't have enough strong mages to nuke an army.