statcounter.com lists MacOS as 15% of global desktop market share [1]. It's a bit more in some markets (25% in NA) and a bit less in others (5% in South America), and anecdotally dominant in some niches (US Startups, EU designers, etc). But I think your point stands that Windows is the overwhelming majority of the market, MacOS a distant second and everyone else barely notable (ChromeOS ranks above Linux).

1: https://gs.statcounter.com/os-market-share/desktop/worldwide