Adding other elements changes the taste,

This is not how chemistry works at all.

To start with, fatty acids also need Oxygen because of the COOH and OH group of the glycerin in fat. They are not hydrocarbons. You know what also is just made of Carbon, Oxygen and Hydrogen? Hundreds of thousands of molecules. All sugars and carbohydrates. If you allow for Nitrogen too, you could cover most molecules found in biological life.

None of this has any bearing on how difficult or complicated it is to synthesize these from more basic molecules like CO2 or H2.