Why am I getting less XP than usual in Fortnite Creative matches?

When you reach a certain threshold of XP gained across all Creative games, you will gain less and less XP for each accolade earned. This happens no matter what the set XP weight of a particular accolade is. If you repeat the same actions or play the same game over and over, this also triggers a steady decrease in the amount of XP earned each time. This is called "diminishing returns" and happens automatically. It is not something a creator can customize or affect.