Music has nearly infinite potential for subtlety, and yes, drums might seem more simple on the surface, but after a few years in music school you'll be tuning drum heads every time you sit down at a snare drum, have a mallet collection that weighs 30 pounds, and enjoy discussing the relative merits of different origin rosewood on your marimba.
Most people have some sense of absolute pitch, even if it's just a subconscious association of things in the key of Bb minor with other things in the key of Bb minor. And yes, in a perfect equal temperament world (i.e. electronic music) every transposition is functionally the same as any other. However, different instruments respond differently in different keys, both as a consequence of their construction (open strings) and despite centuries of work to make timbre as consistent as possible.
However, I think the most compelling argument is the least subtle of all the above, and that is that up until the mid-18th century, classical keyboard music was not played in equal temperament! It was played in well temperament, which, like equal temperament permitted music to be played in all keys, but did not completely equalize every interval, so that every key did have a distinct (and distinguishable) "flavor".