What you are not understanding is that all of this salary cap nonsense doesn't change the fact that he wasn't offer sheeted which, by this fact alone, means that no one thought he was worth offer sheeting. I don't know how you can even argue this point.
All of the reasons you're giving above are PART OF THE REASON HE WASN'T WORTH OFFER SHEETING. Holy crap. It's not solely about him not realizing his potential it's also about the cost, the cap, the contract, and everything else. I'm not ignorant about these things for crying out loud.
You're taking this like I'm saying he's a worthless piece of shit player that's not worth a bag of pucks. I'm saying that no one thought it was worth the risk, whatever that entails, to offer sheet him and that's exactly what happened and why he's still a NY Ranger.