The cards obviously matter, but not as much as the situation (Duh).

For example, I have 8/9s on the BB, folded to player in cutoff, makes standard 3x BB raise, we both have 15bb stacks. Do I shove it in here?

That would be a poor question to ask. It depends on the other factors. I have a great hand for "re-stealing", but pushing only on that merit would be terrible. How has villain been playing? If villain has been tight and passed up on a similar opportunity in earlier rounds, I may very well just fold. If villain has been loose and stealing at every decent given opportunity, but I think he is capable of folding enough to be +EV, ramming it in is fine. However, the cards you are holding obviously affect how you fare against villain's calling range and much fold equity you need for the play to be +EV, and saying they are completely meaningless is rediculous. I don't think Rocky meant it that way, I just think he is trying to say the situation is much more important, which it is. If you wouldn't be willing to resteal here with a much worse hand than 9/8s based on other circumstances, its very likely the spot isn't good for a resteal anyway.