I hear you. No doubt, that MTB is the antithesis of your Madone. So is my 1990 Stumpjumper MTB (non suspension) compared to my Felt 75 (aluminum/carbon). And, I still find it very enjoyable to ride the Stumpjumper on the gravel and paved MUPs.
May have still noticed a big difference had that been a $1,000 MTB donning semi-slicks. By your astonishment, i take it, you don't do any MTB rides on MUPs, especially paved ones?
Talk about weight! I recently picked up/flipped over my 12 yr old son's BMX bike (from Toys-R-Us) to put the chain back on the front ring. Wow! What a beast for such a small bike!
Nice looking Trek!