Comparing a Nexus 5 to an S7 isn't really fair, you're comparing old hardware to cutting edge, of course the N5 is going to suffer.
Personally I think the N5 was a fantastic phone, probably one of my favourite ever handsets. Occasionally when I'm on site I'll pop my sim in to my old N5, it still performs admirably with no lag, I could easily use it as my daily driver.