This was never...a new UI."
Gideon Ansell, Quick Base Director of User Experience, called it "a new UI" at least 5 times at the Empower 2016 Product Keynote. It was absolutely clear that QB intended to change out the UI with the goal of "your same apps running in the new interface" (Gideon's words). He repeatedly says the current "classic" UI is problematic due to inconsistency across devices, it's slow, it's too complex, it doesn't show enough data on screen, and it's not adept at localization (And he's right on all counts). You can watch the video if you don't believe me, skip to 37 minutes in:
https://www.youtube.com/watch?v=CMxu_Hs-f0ISo rewriting history that Quickbase users are perfectly happy with a UI from 2012 staying on for the foreseeable future, and this pivot will all work out great for everybody with two different architectures, is just pure spin.