I think the word "appeal" is a bit touchy. My guess is: there are schools of art, long and complicated theories about which skills to train and what is real art, and what isn't. And then there are those madpersons, who don't give a dime about all that art theory and do something completely different, and everyone agrees, that is just interesting to look at. Off course, there are way more madperson, who don't give a dime about art theory, and their stuff is just boring as heck. The difference is called "appeal".
I think trying to systematically practice "appeal" is a fool's errand. That's like trying to find a course, that teaches you "success"! You will probably find a lot of such courses, but you can be guaranteed each and every one of them has been set up by a con, who tries to transform the content of your wallet into the content of their wallet.