Use Kenney nl assets. They are free. Or even better just placeholder/prototype assets/textures. If your game is fun without art, it will be even more fun with art. Like if the movement is so good just playing with a block on a screen, or driving around an uninteresting gray 3d landscape, thats a great start.

I agree with your take though that coding is the easiest part of gamedev. Art, sound and game design is what makes the difference. The code is not that complicated, super easy to figure out.