People probably could make good sounding music from code, but it's harder. When you're making a new patch on your synth, you don't want to think about complicated matters like code-as-text, you want to be able to turn a knob and hear a difference, with each change getting closer and closer to the wanted sound. Having to write even one line of code instead of sliding a slider up/down would instantly put me out of the flow when I'm creating new patches, no doubt. Changing values to some specific value instead of kind-of-here-sounds-good-to-me would slow down the entire flow as well. Switching between computer keyboard and my synth keyboard just to make a small change would do the same.

All in all, if you know exactly what you want you could probably do it in code, but part of the fun in creating a patch, and what helps with creativity, is experimentation, and I feel like that would easily get lost when coding with strict values and other "computer" syntax that fiddling with a real synth just flows together with the rest of the music making process.

There is no comparison really between the UX of sitting with a computer keyboard in front of a screen, writing/editing syntax to hear changes and hearing real-time sounds coming from something like Novation Summit together with a good pair of headphones, with zero screens involved.