Speaking only for myself, nostalgia it is but not entirely. People who never had an MP won't understand those who did, and vice versa. I bought the 4,1 when I was running a Mini 2014 and an MBP 2008, and the MP was a revelation. Then came the 5,1, then came a 6,1. Of course, it's nostalgia.
Those beasts have trays for four 2GB internal disks plus the PCIe slots for extra disks and video cards. No external stuff, no tens of wires hanging on the floor. Imagine an Intel MBP with all these external connections, let alone its performance.
But, did I say "an Intel MBP?" Apart from storage and lots of RAM, these old MPs are inferior in many respects---pity, but true. My 5,1 is for sale, and soon will the 6,1 as well. In practical terms, I prefer the new Macs.