1 pointPCGW has a mutual linking relationship with IsThereAnyDeal (see https://www.pcgamingwiki.com/wiki/PCGamingWiki:Partnerships#Mutual_linking_relationships). Because of that, any potential replacement would necessitate a similar linking relationship before it would be implemented, I imagine.
1 pointThe point on registration requiring a Steam account is very important. Steam is the biggest store but there are people who don't have a Steam account. Until it's possible to sign up without Steam, it shouldn't even be discussed as a replacement for ITAD.