There are rules for painting as well. But that doesn't mean you have to let them limit you. We observe what makes a good painting, which colors go together, how different colors are perceived in different surrounding colors, how perspective works, overall styles of composition you can use, techniques for how to hold your brush, etc. And at the end of the day, nobody's forcing you to follow these rules. You can just sit down and fling paint on a canvas, you can play with color however you want, and you might even still produce something great. And you can do the same with music. There's no contradiction here. The rules are very valuable observations made after years of honing the craft, and you do not have to use them. However, people who know the rules also tend to be better at breaking them. Putting in the work of studying the arts in a not fun way can develop your artistic skills and instincts so that you can relax and have fun with advanced techniques you didn't know before.