Art is the expression or application of human creative skill and imagination, mostly in a visual form.
This is roughly the definition of art, which typically refers to painting, music, clothing, etc. Meaning that if you see beauty somewhere, something created by a person that to you and many others is art. Graphic design does that! With graphic design, you can create beautiful content, let that be logos or different images based on what you are trying to achieve.
One of the most requested and one of the most desired characteristics you need with graphic design is creativity and attention to detail, which is exactly what art also requires. It's impossible to force yourself to create something beautiful, you have to feel it, and you have to imagine it. No amount of experience will teach you how to do that. No client will ever be pleased with something "robotic" and without passion.
In my honest opinion, graphic design should be considered one of the most creative and innovative forms of art and human expression. Mixing colors, shapes, lines, and details are not easy. Especially when this is done through an electronic device. You have to think differently and outside the box constantly. You have to adapt your knowledge, creativity, and client's needs to what would look good in the website or app.
If you are a painter and someone asks for a portrait, you will mix and match colors. You will add shapes and texture to create the perfect portrait. In graphic design, you will essentially do the same thing. But instead of using an actual brush, you use virtual tools.
Most of the professional and experienced graphic designers that I personally know, are also very skilled in some form of visual art, such as painting, photography, music, or abstract art. That proves perfectly how high creativity levels are linked together in both of the scenarios.