So without being from there, the freakout I can remember seeing in written media about losing that status always came across strangely to me. There are over a thousand unesco world heritage sites, with some in places that are effectively off limits to tourists anyways, so it would be dead weird to have any tourists nearing the banks of the river Mersey as part of trying to tick off the entire list or something, and even though I just spent 13 years working with people who traveled the world, I never once heard one person be motivated to visit anywhere specifically because of that status.
And this is probably going to come across pretty libertarian, but: It's generally going to the for the best if the people from a city make determinations about how best to use its spaces. The further you're removed from the local authorities on that, the more obvious it needs to be that it'd be a mistake for further development on a site; like it's one thing for a city to block building for historical preservation, but if the city doesn't and a regional authority does, that's way more acceptable than an international body with no local accountability whatsoever determining that a city can't develop and needs to be stuck with centuries old ruins taking up key spaces.