Commerce hubs suffer too because gold is less good than other yields. So while I can sometimes get a +4 commerce hub, at the "Standard" exchange rate, that's really only equivalent to a +2 holy site in what they can buy. Those facts mean that more often than not, I simply end up ignoring the CH adjacency and try to fit it to something else.
Probably what commerce hubs need most are for the buildings in them to further expand on the adjacency. So like Harbors adjacency matters more because the shipyard can turn that into production, if all banks acted like the gilded vault and turned the adjacency into culture (or even if the bank simply gave +gold based on the adjacency as a secondary bonus to its normal use), that would help me care more. And then you probably still need a few other standard or major sources - ie. if all districts simply gave a standard adjacency instead of a minor one, or if city-centres gave a major boost, or even as people have mentioned, if a commerce hub generated 1 gold for every trade route that passed through it, then they would become more valuable.
Probably what commerce hubs need most are for the buildings in them to further expand on the adjacency. So like Harbors adjacency matters more because the shipyard can turn that into production, if all banks acted like the gilded vault and turned the adjacency into culture (or even if the bank simply gave +gold based on the adjacency as a secondary bonus to its normal use), that would help me care more. And then you probably still need a few other standard or major sources - ie. if all districts simply gave a standard adjacency instead of a minor one, or if city-centres gave a major boost, or even as people have mentioned, if a commerce hub generated 1 gold for every trade route that passed through it, then they would become more valuable.