There are really only a handful of ways to handle this.

• Find an artist to work with you. This can be challenging if you can't pay them for their work, and in most cases you'll end up spending more time trying to find someone than actually making your game.
• Buy pre-made assets. Again, this is only viable if you have the up-front capital, and even then it's hard to find all of the assets you need in matching styles.
• Use free assets. No cost, but you typically pay for that in terms of quality and how well the assets meet your needs. It can be done, but you may have to tailor your game's design around what's available rather than what you wanted to make.
• Learn to draw. Depending on what kind of game you're making, this might be viable in the short term, but more than likely it will take you years of dedicated practice to be able to produce the quality of work you want in your games. I've been drawing casually for twenty years and I'm still not great at it, it really takes a dedicated effort.
• Make games that don't need art. Rely on your strengths as a programmer to solve your visual dilemma. Learn how to write shaders, focus on your lighting system, or write an algorithm to create procedurally-generated art. You can make things look great without any complicated art assets at all, just look at Thomas Was Alone.

If you really don't have the time (or drive) to learn to do your own art, and you're on a shoestring budget with no artistic partner, then I highly recommend the fifth option. Thomas Was Alone looks amazing with just rectangles, particles, and a subtle lighting system. Cube & Star uses simple geometric shapes and good lighting to great effect. There are tons of games that look great with little to no art assets. If the game you want to make won't work without great art, then maybe you need to shelf that game idea until you have an art budget or find someone to work with. There are plenty of game ideas that can look great with no art, there's really no reason to let a lack of art stop you from making a game.