> Proof of work's security properties are broken for everything that isn't BTC, ETH (although this will change soon) and whatever the dominate CPU coin is

PoW secures any coin that dominates the daily issuance of all coins (efficiently) using the same hardware. So the different hardware classes are

CPUs

GPUs

SHA256 ASICs

scrypt ASICs

Equihash ASICs

X11 ASICs

etc...

and each one can secure one dominant coin.