Huge difference in difficulty between World class and Legendary is abyssmal

So tell me why I can you know beat a team on legendary 90 rated 33 chem roughly what 10-0? but when you know i wanna take a break (if you can even call it that on world class) for some easy gameplay and relaxed tell me why they all of sudden act like ultimate AI? and trust me i know theres something between ultimate and world class seeing as i can do ultimate difficulty and i can quite easily say theres so many similarities in ultimate and world class its wild i genuinely almost seems as if your wanting people to just stick to Pro and lower