Yeah 7.1.2 was by no means perfect. Still had hiccups, particularly on iPads. I don't think iOS has ever been in a finished/polished state for iPads since iOS 7 dropped. I only glorify iOS 6 for its smoothness and some little UI elements I preferred. But the flat design is far more modern and versatile now.
iOS 8 was smoother than 9. iOS 8 and iOS 7 were both fairly smooth, with 8 being a little worse but still not nearly as bad as it is now. iOS 8 was just more of a slop bug mess, PARTICULARLY in the earlier stages (pre 8.2). It was never fully resolved to the less buggy (note I did not say non-buggy or bugless) iOS 7, but 8.4.1 was still fairly good. iOS 9 added a bunch though and made everything into a sluggish stutter fest.
That's my opinion, trying to be the least biased I can.