The deal with the bourbon isn’t necessarily that it be top-shelf, it’s that it fits the profile of the beer.
Makers Mark is a fine whiskey bourbon but aged six years it may not have the flavor profile necessary to blend well with the beer.
JBB, a straight bourbon, is aged 8 years and when added in the right quantity has a flavor profile that enhances the beer.
Now, if you can actually taste the whiskey you may have added too much as one would think that MM would work equally as well as JBB.
If you make the beer again, try using less whiskey or scale the amount of whiskey you use by adding 1/4 teaspoon increments to glasses of beer until you reach one that fits your liking.