Well, it's always possible your palate is stunted.
Really the only way to get there is practice. Use a rocks glass with only a finger or so of bourbon, neat, so that the aromas are concentrated under your nose (olfactory is at least 70% of taste), let each sip roll around a bit and drain gradually off your tongue before swallowing, then breathe in to maximize the finish. Concentrate. Relax.
The flavor descriptions you hear are all approximations, anyway---vanilla, cinnamon, caramel? Not actually there, just something reminds the reviewer of that. There are some REAL flavors, like 'char' (from long, long barrel time) and 'copper' (from traditional stills, like Willet's. You can REALLY taste the copper in Willet's) and one I just call "corn" because it's in bourbon but not Scotch, and it's slightly sweet, so I figure that must be what it is.
You'll come up with your own descriptive language eventually. And remember, the most
important one will always be along the lines of "Now, that's some DAMN fine Bourbon!"
~Boar