a 2012 machine is more than acceptable as a builder, heck my mother still uses a 2009 MacBook pro and she uses her laptop quite "heavily" (She never closes programs/browser tabs), my mac pro is from 2013 and it's perfectly capable.

But, I think my pedantry does not dissuade from your actual point; making a modern MacOS program requires that you have a macOS machine- It also precludes learning a language that typically only runs on that platform (I know swift is cross platform but none of the windowing libraries that you'll use are).

Making tailored software per platform is tedious, making the same program multiple ways so that it can be native is just time consuming if nothing else.

Electron is an ugly way of fixing that; but it does the job of fixing it- Qt is an ideal solution in theory but it's obviously too much of a burden on developers to adopt.