Is describing the Quranic surahs with a derogatory word considered a disparagement of them, even if the intention was not to mock the short surahs?

Your description of the surahs as "short" does not negate your faith if you did not intend mockery by it, but it may be a lack of manners. We advise you to abandon obsessive thoughts and increase your seeking of forgiveness. Your description of your lack of excellence as a result of injustice contains no harm, unless you accused the correctors of injustice without certainty, and its expiation is seeking forgiveness and repentance. Interpreting your words as an objection to God is very far-fetched. You must abandon obsessive thoughts so that they do not lead you to madness.