I feel like the branding really shot it in the foot. If they'd named it something less "startup-y" sounding, and marketed it as secure, instant transfers backed by the banks themselves, they might be in a better position.
I still use it all the time since it's a superior to any other offering for instantaneous high-dollar transfers, but it always feels like a "Venmo got embedded in my banking app" type of interface vs. "my bank is offering a direct payment service to it's other networked banks".
Hard to define, but I do think the marketing/branding/rollout were more to blame than the merits of the service itself (IMHO, Zelle is great).