I like base 12 a lot, but Reverse Polish Notation is a mess when you get up to working with polynomials.
With polynomials, you're moving around terms on either side of an equation, and you combine positive terms and negative terms. In essence, there's no such thing as subtraction. (Similarly, division is a lie; you're actually just working with numerators and denominators.)
Reverse Polish Notation makes that a mess since it separates the sign from its term.
Also, RPN draws a distinction between negative values and subtraction, but conceptually there is no subtraction with polynomials, it's all just negative terms. (Or negating a polynomial to get its additive inverse.)
But, yeah. It's a shame we don't use base 12 more.
What base 12 gives you is a lot of common divisors: 2, 3, 4, and 6. Base 10 only has 2 and 5. Base 16 only has 2, 4, 8.
The practical upshot of this is that you can divide things evenly in more ways. Particularly when wanting to divide a board into thirds. Having 12 inches to a foot is actually helpful there, though it falls apart as soon as you get larger.
Base 16 is great when you're interacting with a computer, but aside from that, not much. Only being divisible by 2 is kind of a pain in the real world.
Both are easily countable on fingers using your thumb and counting up the segments for base 12 and adding the pads for base sixteen. You can reasonably count to 144(gross) or 256 using both hands to create a two digit dozenal or hexadecimal number.