Fwiw I don't think there's anything inherently sequential about the Keccak permutation itself. KangarooTwelve is a fully parallelizable hash built on Keccak. (Though they did use the sponge construction on the XOF side, so that part is serial.)
CShake128 is much better replacement for hmac and sha512 in (zk)proofs, while Kangaroo for things like FDE and massive volumes of data.