Serious question, why is this a "bad" complaint? Personally I hate transitions, I think they bring nothing of value and they're wasting my time, had the impression that there must be other people who thought exactly like me.
You might be surprised at the hints they give you subconsciously about where UI elements are going and what they're doing. Google's Material Design actually does a good job showcasing this - I had no idea the lock screen had a 'double swipe' motion to bring down quick toggles, but the transition of my first swipe made it clear that the extra motion was available to me.
Proven how? With first-time users? Phones are things where I want to pull it out of my pocket, do the thing I want to do, and have it take the absolute minimal amount of time. I don't think this is a techie thing. Even non-techies are willing to take a little more time to learn an interface if it means they can spend a few seconds less to send a message. That said, if I have a device that can send a message quickly, I don't want to pull it out of my pocket and find out I have to re-learn how to do it. I don't care if the interface is better - I want a 5-year interface, not a 5-month interface.
When you make statements like "helpful for users" you can't stop at a simple focus group. You have to think about how added complexity hurts the reliability and speed of the device.
It seems standard that phones older than 1 year are getting slower and slower. I've had the same Android phone for about 22 months, and it's been getting unusably slow (mostly, Google Apps (Gmail, Maps, Hangouts) take between 10-15 seconds to open on a white screen.) I'm willing to believe the hardware has degraded over the time I've had the phone. But primarily, I think software has been pushed out that was designed for flagship phones released in the past 8 months without looking at the performance impact.
This is not the kind of innovation we need.