I've been playing around with low-level Metal a bunch lately, any many of their docs and samples seem still be mostly in Objective-C/C++ and not Swift, so have been forcing myself to get into it.

At first I had the usual revulsion to the syntax, but after a few days getting used to it, I actually don't mind it at all now. (I still wouldn't say it's "elegant", but I can live with it).

Being Metal shader code is basically C++ anyway, and C++ is a language I'm familiar with, having a couple of .mm files to hold the Objective-C++ for API bridging and working in regular .cpp (and .h) files for the rest is pretty straight forward compared to having to learn Swift. (Especially with all the complaints I've heard about its complexity, including from Chris Lattner himself lately, which aligns with some of the other comments here).

Though to be fair, "Swift seems overly complex so use C++ instead" seems like a tough argument to make with a straight face ;-p