GIMP still only half-supports CMYK in 2018, though. But as someone who uses it professionally, I agree that GIMP is a Linux's Photoshop, not a Linux's MS Paint. I'm guessing that the user you replied to has only used it as such and hasn't dive into all the tools and features it offers. With all the bugs and half-broken tools it has, I still think it is a great piece of software, and my life would be much harder without it.