I would expect he has the same issues with Cap'n Proto. Aside from some aesthetic cleanups, Cap'n Proto's type system is extremely similar to Protobuf -- because, frankly, Protobuf got that part right. Cap'n Proto's main difference from Protobuf is the encoding, which it doesn't seem like this guy cares too much about.

(I'm the author of Cap'n Proto, and Protobuf v2, though I did not design Protobuf's type system.)