If it was a Str of 20 would everything about this stat block be perfectly fine and you'd have no problems? If yes then I feel this is making a mountain out of a mole hill.
Of course 20 vs. 21 wouldn't make it "perfectly fine" for me. But I admit that the 21 does annoy me, meaningless though it might be. Maybe
because it's meaningless -- they can't have made this NPC superhuman for gameplay purposes, because it barely affects gameplay. So then why is this dude theoretically the strongest humanoid on the planet? Isn't that a least a smidgen weird?
Maybe I'm making a mountain out of a molehill anyway, because I've always believed gameplay beats realism every day of the week, so maybe this barely matters. But that doesn't mean realism means literally
nothing and should be completely ignored. Some people in this thread are acting like Keith has no valid point at all, that's he's just a "hater", but I think he undeniably is onto something. Maybe it's a major objection or maybe it's a minor one, but either way it's a valid enough point that it shouldn't just be ignored.
Most Campaigns end at around Level 10 or 11, if not earlier. So CR 10 is fairly top of the line. There is no stat block for a "King of the Dwarves"...and in fact the Warrior Commander would be an excellent fit for a Dwarven King.
CR10 is barely a speedbump for an adult dragon, much less an ancient wyrm. Whether that's fitting or not depends on how you imagine a dwarven king, I guess. When I hear "King of the Dwarves", I think of a legendary figure like "The Dwarf King" of 13th Age who is a literal icon. I very much assume that dragons would flee from
him, not the other way around. Obviously another person's imagination may vary on this topic, which is fine, but to me "warrior commander" feels more like a captain of the guard, not legendary monarch-champion. If the guard is a superhero, how high do the stats have to be for my vision of the Dwarf King? Does he need a STR of 30? If he does, is this game still on the rails, or are we playing Calvinball?
What you have a problem with is not this individual NPC’s stats. What you have a problem with is the entire concept of a generic NPC being CR10.
You might be right. That kind of thing never sat well with me in 4e, and I really liked 4e. I was always a little uncomfortable that some 4e orcs were suitable foes for a 1st level party while other orcs -- again, not legendary figures, just typical nameless grunts and guards -- could easily slaughter that entire party by themselves. However, at least there were obvious benefits to that lack of realism and scale. For example, combats against a solo monster worked much, much better in 4e than in any flavor of 5e, and balancing in general was solid and easy. That being so, I accepted the peculiarity with levels and stats as the price we pay and let it slide. I can still let that kind of thing slide in 5.24 if I must, but I'm not clear what benefit we're getting from the superhuman Warrior Commander that justifies throwing the 3-18 stat scale out the window.