There a 3rd level monk class feature called Deflect Missiles that works mostly the same way. The main difference is in the attack added to the reaction: Deflect Missiles lets you attack anyone in a close range while Blocking Wings only allows you to hit the same creature that attacked you. I do think that Blocking Wings is stronger though, just because nearly all creatures can make melee attacks and relatively few carry ranged weapons.
Yeah, okay, that's weaker than I intended. It's even weaker for a monk, since they can already run up vertical surfaces and along liquids by this level. I feel like have a "acrobatic/crane form monk" that never gets flight would be really weird, but the basic monk chassis kind of interferes with making it useful.
Would 10 minutes of flight for ~2 ki points work better?