If you dont mind adding more stuff on the outside , you can treat it like a hole in a sailboat ..

sand the area rough , apply resin* add more Cloth ,Carbon fiber cloth. maybe fiberglass will do and saturate it

in *Catalyzed Epoxy ,
push out the air bubbles and let it cure , it will be a lump on the outside , but it may live a little longer .


probably RD, A NEW RD hanger , a chain and likely as the wear of one effects the other, a new casette too.

Of course this is just a Remote guess , from someone where there are a lot more Boats than carbon fiber frame bikes.