To me that reads as though you have too much fat in the recipe be it butter, or shortening, but I don’t know your recipe.
I read a post about too high a heat, but that usually makes for textural difference than thickness. For those that use multiple cookie/jelly roll sheet pans be sure to be consistant with type. The type of pan will effect the outcome of your cookies. Aluminum will make lighter colored cookies that are softer, and the dark stamped steel sheet pans will make your cookies darker, and crispier in the identical amounts of baking time at the same temperatures.
Two sticks of butter. I’m going to try butter flavored shortening and cut back by 1/4 on that. Thanks for the tips.