Limitations force you to think inside the box, but better.
When you are free to do anything, you can sometimes fall into a state of Target Confusion and wind up producing nothing. If you do produce something, you may skim the often-trode surfaces of many topics, and wind up saying nothing no. Limitations, either real or artifical, force people in creative endeavors to think deeper. To work around limitations storytellers, artists, and comedians come up with incredibly creative solutions.
If you’re wanting to flex your creative muscle, you may not have to try something entirely new. You may just do something you’ve done before, but with a new limitation.