The WHC itself still had miles more credibility than any title outside of the WWE title (not saying much). Just look at Ziggler's title winning moment, for a guy like him who'll most likely never win the WWE title, what other championship could have provided him a moment like that? People absolutely did care when he won it, and just because ADR's final reign was god awful doesn't mean the title had lost all credibility.
Hell, it could have been great in The Shield's storyline. If you'd had Dean win the strap a few months ago, with Seth and Reigns cheating/interfering in his matches so he kept it until 'Mania, they could have had Reigns's big moment where he wins the WHC. Sure, he'll most likely still get big pops and a lot of momentum from his win at 'Mania (under the assumption that he does win), but it could have been a much more significant moment in his career if he'd won the belt and then carried it for a few months.
I don't think the unification has given the WWE title anymore credibility, all it's done is remove their second most important title. I also disagree on the brand split, there's easily enough depth - probably more than in some years where the split was in place - they'd just need to improve their booking of certain guys.
