Why no option to accept or decline a challenge?


When you create a challenge, the system will try to automatically find a valid pairing. You can't decline a challlenge you requested. You can decline one when someone challenges you.
If the same person grabs your challenges, for ones that aren't auto matched, you could temporarily block the so they can't.

Thank you! Somebody was playing well above their rating and obviously saw me as convenient low hanging fruit ripe for picking! So, temporarily block a particular player.

Block them.