Per above, it's all about what's important to someone. "I shouldn't buy something because it's old" is actually an example of emotional reasoning, so I have to give kudos to people who are able to overcome that kind of cognitive bias. (I can't, personally, even as someone who recognizes it.) If a 2015 model makes someone happier, and that person truly understands the pros and cons, far be it for me to tell them they shouldn't buy it.
Don’t get me wrong. I considered buying the 2015 model in 2016. I loved my dad’s 2015 MBP. Mag-safe, the I/O, battery life and yes even the lit up logo were all things I really liked. The problem was spending over $2k for a machine which is no longer the latest. I ended spending $3k and for that I expect something that will have resale value. While they really shouldn’t have killed MagSafe it is pretty convenient to be able to charge from either side. The potential of TB3, the P3 display and the stupid fast SSD (for 2016) also had me sold. These drives were really impressive when they launched. Of course SSDs will keep improving but the ones in the 2016 models were substantially faster than the 2015s. Like ridiculously fast. While High Sierra has increased boot time by several seconds, I couldn’t believe this machine was ready to go in about 15 seconds after signing in. I was coming from a machine that took about a minute before before I got to the desktop. I understand that the difference isn’t as dramatic from someone coming from a 2014 rMBP and honestly if I had one or a 2015 model, I would’ve never bought the 2016. I’ll upgrade to a new 15” once these have hexacore core i9s and 32GB or LPDDR4 RAM. They’ll have the CPUs fairly soon but I expect the RAM in 2019 or 2020. My AppleCare expires 12/19 so I’ll probably sell it before then before it’s value is well under $1000. If the resale is too low, I’ll just keep it as a backup. It’s always good to have something in case you have problems with a new machine. I bought a cheap Windows notebook recently just to have something useable in case I send the MBP for a warranty repair.