Yes! You can use bronzers as foundations but it would be a bad idea. Powdered bronzers are supposed to be a finishing product that gives the illusion of a subtle tawny glow. They're not formulated to provide sufficient coverage for imperfections or to correct uneven skin tone.
Using a powdered bronzer as a foundation will most likely leave your face with a greasy texture and an unnatural hue. The natural oils in your skin will absorb the bronzer, leaving unattractive splotches around the face, ultimately defeating the purpose you intended it for. Self.com has great a great article that will take you step by step through using powdered bronzer correctly.
Liquid bronzer, on the other hand, is far more versatile. It can be used alone, and even though it won't give you the full coverage of foundation, it will give the illusion of a natural sheen around the face. This is a good option if you have clear, normal, or dry skin. I wouldn't recommend this if you have acne-prone skin.
According to makeup.com, the best of both worlds is mixing liquid bronzer with foundation. It's best to use a lightweight liquid bronzer formula in an equal dime size amount to your foundation. This will give the bronzer the base it needs to provide proper coverage for your skin. Using bronzer this way is an excellent solution for people with blemished or dry skin.