Concealer is my best friend and I honestly don’t know what I would do without it. The point of concealer is to conceal your dark under eyes, blemishes, imperfections, and reduce redness. But I’m going to go out on a limb here and assuming you’re applying it totally wrong.
Most people dab a few single dots under the lash line and rub it in but that’s not the "correct” way to apply concealer. When applying concealer, you should make a filled-in triangle under your eyes then use a beauty blender/brush or finger to blend everything into your skin. Applying concealer in a triangle shape will make your face appear brighter and more alive.
Personally, I love the triangle method concealer trick because it’s an easy way to illuminate my eyes - it conceals my dark circles and brightens my face.
Ps - Before applying any concealer (or face makeup for that matter) you should hydrate and prime your skin. So make sure to apply moisturizer, and/or eye cream, and then once it sinks in apply primer to help makeup last all day long.