I love MIDI files as I use them to practice my guitar and piano skills. But rock MIDIs always sound as if they are being played by a blind beggar with a cheap Yamaha organ on my local street corner. Oddly, jazz piano MIDIs (at least to my uneducated ear) sound OK
Now I can guess some possible reasons - guitar sounds not accurately represented, poor transcription by the author. But is there any fundamental reason why a MIDI couldn’t sound better?