Not just the visual appearance, but for example keyboard shortcuts are relatively universal; Cmd + , is the shortcut for Preferences/Settings in Safari, Chrome, iTerm, Slack, NewsReader etc. I don't know if that would even be possible on the leading Linux DEs.
I love the customizability of linux, but I've decided that a good user experience goes beyond the appearance, and what's required is putting serious thought into user workflows. Those sorts of usability studies don't seem to be a priority for most FOSS projects.
There are things about Linux that I miss on Mac, but overall I prefer a system that's consistent to one that ticks every single box.