The latest macOS updates have me pining for macOS Mojave. I really liked that release - first-class dark mode support that felt reasonably polished, it still had a "normal" Mac OS X style UI, 32-bit support if you wanted it, it was snappy even on my 3 year old 2015 MBPr, and I think it wouldn't look out of place on a modern M4 Mac even though it's a seven year old release.