I'm not saying you need to be a top run team, but you need to at least be competent. The steelers simply aren't right now. If you are honest about the steeler run game, generally they break a couple of decent runs per game but the rest are pretty much stuffed for almost no gain. Those few good runs make the overall YPC look much better than it is.
Mahomes adds a run threat that Ben doesn't. Chiefs averaged 4.2 per carry last year and 4.4 this year which is pretty good. Last year the steelers averaged 3.7 and this year 3.9 which is pretty bad. As i stated, that is a concern.
It's not about overall stats though. It's about situational football. The simple fact is that 3rd and 2 in a key spot for the steelers damn near has to be a pass. Defenses know this. When the Chiefs are in 3rd and 2, the defense has no idea what's coming. Mahomes can fake it and run it himself at any time and that keeps the defense honest.
Mahomes does indeed add a run threat. And his runs make the Chiefs YPC look better than it really is. Actually Mahomes has been running a bit less lately, though he reminds me more of a (very) young Ben where he creates big plays downfield with his elusiveness. Ben is the opposite of his former self now, getting the ball out quickly and moving the chains with the short passing game. And it's working.
Ben's been sacked only 10 times in 10 games. 4 out of the last 5 games, he hasn't been sacked even once. This line is doing the job in pass protection, and when outcomes have been in question, the Steelers' offense moves the ball through the air to secure victories. Just like the Chiefs.