I'm hardly an expert. But it is hard for me to escape the impression that the original sin of Apple's mac lineup was to go all retina as early as possible, instead of aim for incremental improvements in screen quality that would allow them to hold onto performance and battery life. On the Pros, it took 2-3 years of retina screens before I felt that that the day-to-day UI performance could hold up to an anemic non-retina Air, even as the multicore performance went up and up.
Now even 6 years out, we are seeing that it remains impossible to build an Air-like machine that keeps up on performance and battery life around a retina screen. (Again I am not an expert, but it seems like Intel's inability to keep up also has something to do with it). So we've probably hit our target battery life, in a near-perfect sized chassis and screen, but on an anemic netbook+ for performance.
Non-creative white collar types and students need a device with a light footprint, excellent battery life, and the power to keep up with normal day-to-day multitasking including some technical computing. It sounds like this still, despite all the hype, isn't it. The nTB with longer battery life, or this with a 1080p screen and a 15w cpu, probably would be.