2017 may be significantly better that 2011, but it's NOT significantly better than the early 2015 Retina's.

The problem Apple has is that the early-2015 Macbook Pro Retina's really hit the balance point with the physical form factor. Enough heft to feel solid without too much weight. Enough battery life to do real work. A solid set of ports: HDMI. Magsafe. USB 3.0 ports. A keyboard that doesn't break due to random micron-sized dust particles.

So, a LOT of people want a 2015 Macbook Pro but with ONLY the tweaks to bring it forward to 2019 technically (memory, CPU, display, change to the two Thunderbolt 2 connectors to USB-C Thunderbolt 3) while leaving it in 2015 physically.