Yes I'm aware of that. But regardless of whether you mean this in the sense of adapting to user stylesheets or the idea that disparate elements' font sizes should relate to each other, they both strike me as maintainability trade-offs that can reasonably go either way. An elitist tone seems a bit unnecessary in that context.

The font size can change due to zoom, which is a must, because 16px is too small text and unreadable.

cmd+"+" has always worked regardless of what unit is used, though?

Elements measured in pixels (like images) don't change size when text changes size.