When Apple launched the current MacBook Pro design in 2016, it kept the old 15-inch model around for those who insisted on the the earlier design. Now that the 2018 refresh is here, though, that holdover has gone away -- the 2015 MacBook Pro is no longer available through Apple. It's not a surprising move when the system was three years old, and its performance was clearly going to lag behind cutting-edge six-core models. However, that's not likely to please some people. Unlike other legacy models, there's still a significant contingent pining for the old model.
Apple has steadily addressed complaints about the butterfly switch keyboards on the current MacBook Pro design. The 2018 models in particular promise to be quieter than before. Many, however, still prefer the travel and overall feel. Moreover, the jury's still out on whether or not 2018 Pros' keyboards are any less failure-prone than previous iterations. With the 2015 computer no longer available, you have to take that risk if you want to buy a new-in-box Mac laptop.
And then there's ports. While it wouldn't have been trivial to put more ports into the current MacBook Pro chassis, it remains true that many, many people miss the SD card reader, the HDMI port and the MagSafe power connector. And while the USB-C/Thunderbolt 3 peripheral situation has improved substantially since 2016, there are still quite a few devices that don't use those ports or include the necessary cables (including the current crop of iPhones and iPads). Like it or not, you'll now have to deal with dongles, adapters, and not-so-trip-resistant power cords. The 2018 MacBook Pro may be dandy -- it's just that some will still see its design as a step backward, which hasn't usually been the case with past updates.