Not what I hate (and not representative of every modern pin), but what makes them so NOT like a good classic pin:

1) Long ball times
2) Complicated rule sets
3) "Art"
4) Fit & finish
5) Value

Contrast that with countless classics: Brutally short ball times, straight-forward rulesets, art that told you someone really gave a damn, outstanding build quality (think early 80's, 70's, 60's and before), and value that said you got more than what you paid for (from an operators perspective these were huge revenue generators). I can't speak from personal experience on the last point, but considering how few pins are routed now versus then tells me that this is self evident.