D&D is merely a ruleset, a framework for a DM and their players to utilize in order to (hopefully) have a good time together. Usually the DM interprets that based on their current players and the campaign is rarely ever fully RAW in my experience. Nowhere in it does it say humor isn't welcome in its campaign nor systems, if the DM deems it so. Besides, humor is about as subjective as it gets. For example if you were to ask me, by that logic Bard shouldn't exist, as it's too humorous for D&D.

Can we stop mixing up subjectivity and objectivity, please?