You do realize that Birthright is more the Byrne version of Superman than Silver Age right? The fact is, ALL the complaint I've been seeing is how continuity is effected. Is Birthright Elseworlds? Is it a Retcon? If it is a Retcon how will it effect the post-Crisis stories etc?
People didn't stay away because it wasn't a xeroxed copy of Byrne (which you need to get off of the idea Byrne has some cult of followers because it aint true), the reason so many people stayed away is because DC refused to give a solid answer on anything.
Or maybe, just maybe, people didn't like it. Or maybe, just maybe, people liked Man of Steel and felt they didn't need to read a rewrite of a story they felt was written well in 1986.