Bard is today what Thresh was back in seasons 3, 4, and part of 5. He's the posterchild, the chosen one, the "Hey look, support can be fun" guy. He's very popular... among support mains. Which League has a significant lack of. And just like Thresh, he's not enough to carry the role on his own shoulders. People haven't started playing support just to play Bard; at least not in numbers large enough to save queue times.
Speaking of Thresh, he was on his way out before Bard came and took his spot. He was really something back in season 3 when he debuted with that overloaded kit and his jack of all trades playstyle. But as other champs debuted or got reworked to have more and more tools in their kits as well, he began to be less and less special. He's not really that big of a deal anymore.
Braum seems like he's popular, but players like the idea of Braum rather than actually playing as him. People love Braum... but when's the last time you saw someone actually play him? I saw one (attempt to) go top lane a few months ago; before that... I honestly can't remember. Players want his upbeat attitude, his manly punching, his love of poros, and his godly facial hair. They also want him not to be a support so they can play him in roles they enjoy. That's why when he first debuted he was like Kench; played top, mid, and jungle in addition to support. After he was nerfed to keep him in bot lane, his playrate fell off dramatically.
Same with Taric, his rework made him popular for a month or so, then people realized that "Oh crap, if I want to play this guy I have to support" and then he settled at the bottom of the popularity list. (That's not completely true as I do enjoy taking Taric top lane, but I would never claim it's standard play)
It's a pretty clear message: It doesn't matter how cool a support we construct, the hype will die down quickly as long as the support role is in the shape it's in. We can extend this hype and artificially increase sales by releasing the champion overtuned enough that they can go to more popular roles; but once those sales start to slip those champs receive a beating from the nerf bat. That's not a great way to do things.