Here's why:
* Adverbs describe actions or adjectives. They tell us *how*, *when*, *where*, or *to what extent* something happens.
* Comparative and superlative forms are used to compare degrees of a quality. For example, "fast" becomes "faster" (comparative) and "fastest" (superlative).
To express different degrees of joyfulness, you can use other words or phrases:
More joyful/less joyful: These are common ways to express degrees of joyfulness.
More joyfully/less joyfully: These are more formal ways to express degrees of joyfulness.
With greater joy/with less joy: This emphasizes the feeling of joy.
More happily/less happily: This focuses on the outward expression of joy.
Let me know if you have any other word you'd like to find comparative and superlative forms for!