Benchmarks can be misleading. In real life usage the 6s is only slightly slower than the 11. Definitely still a good phone. I heard that it may receive iOS 14 (we'll know for sure if it'll actually be the case during WWDC 2020).The 6s is a great phone, I just upgraded to it last year.
It's got a real home button, headphone jack, is plenty fast enough... It's pretty much the ideal iPhone.
I'm putting it in the same category as the 2012 15" MBP, the best Apple has ever built. It's only gone downhill since then.
I loved my 6s but had to give it to my parents. Their 6 was on its last legs last September (yes they share a phone). If this weren't the case then I would've carried on using the 6s instead of upgrading to the 8+. I'll probably use my 8+ until it breaks. No need to spend extra cash on a new phone when my current one works plenty well. I miss the headphone jack, but Belkin's Lightning Audio + Charge splitter suffices. To me it's better than spending money on AirPods which require regularly charging, are relatively easy to lose, and uses up some battery life (Bluetooth).
Lastly, not sure about the 15" 2012 MBP, but the 13" one is the final MacBook model with a CD/DVD drive I believe. Definitely a feature that some (or even many) people still prefer.