system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What are sushi masters doing that is so masterful?

I know this is kind of an ignorant statement (this post is my attempt to combat that ignorance), but I watched documentary on a sushi master, and it looks like he takes a piece of raw fish, combines it with a clump of rice, and brushes it with a little sauce. And it apparently took him 30 years to master that, and he's still learning.

What about that takes decades to develop, and how is it different from someone with less experience combining the same handful of simple ingredients would produce?
gpt
it starts by the chef choosing which fish to buy from the market.   is it a good fish?  a great fish?  what parts of the fish are good.  what parts are great?   

once the fish gets to restaurant,  how do you cut the fish?  what angle 
 do you cut it?  what's the action of the knife cut?  which parts of fish fit which dishes?    

alot of making sushi is in the making of the rice.   what kind of rice are you using?   how much water?   what temperature?  how long are you cooking?  how much rice vinegar are you mixing in?  how quickly are you cooling down?  is the action that you're stirring in the rice making it more or less fluffy?  sticky? chewy?