What is it that you are trying to do with the screws such that they aren't long enough?
Those look like pretty standard fan mounting screws to me. You screw them into the holes in the fan from the other side of the panel you're mounting the fan to. They only need to be long enough to "grab" when you tighten them down; they aren't intended to extend all the way through the holes in the fan. They're held in place by friction (like a wood screw), so yes the fit is going to be fairly tight.
If you're mounting the fan to a thicker panel or if you'd just rather use regular screws and nuts that's certainly an option; but in that case you need to provide your own mounting hardware.
Nostalgia isn't what it used to be.