I've heard this over and over — that Macs are locked-down, uncustomisable machines — and I don't agree with it at all.
I use replacements for almost all the built-in apps. I use a custom launcher. My editor config Git repo is approaching ten years old, and my shell config Git repo is almost eight. There are standard interfaces to per-application Preferences and keyboard shortcuts. When I sit down to use someone else's Mac, I have no idea how to use it!
What changes am I missing? The only thing I can think of is that I can't use a different window manager or a different kernel, but I'm fine with those already.