NES music was my first exposure to music. Not just music, but genres and styles of music.
For a lot of those NES composers, they had to interpret real life music through the NES limitations as a necessity. Whether it be classical, or rock and metal, or jazz, or anything else. They had to take what they knew about music, and cram it in to a set of limitations that had never been imposed before. It took them a while, but eventually they started to learn how to maximize what can be achieved sonically, and they were able to obtain richer and richer sounds. Those techniques became tools you could use to better interpret real life music through the NES.
This is what makes chiptunes such a special thing. There is both an instrument and a genre aspect to them. The sounds themselves can inform the music that is written, or the sounds themselves can be a way to interpret other types of music. But in the end, it all stems from the presence of limitations.
Those limitations are dramatically absent in modern music. Where you can load up a synth and have 100 detuned saw waves for the biggest super saw ever. There is no care or craft or texture required any more now that it can be automated. This is not necessarily a problem for a composer, because by and large, the sounds can still inform and inspire. But chiptune as a genre is something that is much harder to understand if you do not appreciate why those limitations created the nostalgic sounds in the first place.
So, the art in chiptune, from my experience, has been in understanding what made that original gear special, and being able to interpret my ideas through a self imposed protocol to imagine new sounds in old ways, or old sounds in new ways.
Similar to attempting to make a painting with one colour, you will have to make concessions and interpretations for how something that needs more then one colour would look if you only had one. That pursuit more than anything else is the art, or is the reason why I enjoy chiptunes. It doesn't need to be limitations either. it just needs to be imagining something through something else. The abstraction shows everything you need to know about the artist.