Indeed, but if you listen to some retro game themes, you'll notice the synths they used were a lot less harsh, and still followed baselines of music theory. What program are you using for music? If you want to learn a bit about making retro music, this video can be really useful:
Undertale's soundtrack manages to sound retro by using soundfonts in FL Studio, and it produces an absolutely amazing end result! I'm not saying you have to copy what he did exactly, but it can be great for future experiences :)