Yes, generally they're some combination of overly complicated technically, difficult to use without layers and layers of heavy dependencies, are poorly thought out, or solve Google-specific use cases.
Well, the complexity is a problem, but I don't really see that as Google's fault. The only chance to evolve the network is by building on stuff that works despite all the hostile middle boxes, and that necessarily requires quite a bit of complexity, unfortunately. In the long term, it seems to me like QUIC is a better idea than everyone individually having to work around idiocies all over the internet, as that is not exactly a zero-complexity game either.