I think one of the factors has always been the sheer size of DC and Marvel. The larger the fanbases, the more divided the fanbase can get. Nothing wrong with that, everyone is entitled to an opinion and there's still plenty of good things at DC and Marvel. But Valiant can be a shared universe small enough that one doesn't have to spend literally hundreds a month to know everything. Not being divided into editorial "offices" (i.e. the Batman Office, the Avengers Office, the X-Men Office) probably helps keep the universe consistent, even with different tones from Harbinger to Quantum and Woody.