I think godisawesome is right....about the DC of decades past. When Superman was their central figure, yeah I feel like you could kinda gauge DC's overall performance by how well Clark was doing. Just in a very rough ballpark kinda way, of course. But Clark's not the center of DC anymore, and his books don't seem to really affect anything outside his editorial group.
I don't even think we can really use Batman to judge either, because DC funnels 99% of its best talent through that franchise to the point it becomes a statistical outlier. The rest of the company has sometimes been a dumpster fire, but the Bat books were still (at a minimum) decent.