First off, your post wasn't about machine-id, it was about systemd using machine-id, yes? If you think machine-id is a mistake, blame Linux, not systemd. This is a shift from your original claim.
Second, I've already explained my argument many times. Machine-id was likely a simple solution to a few problems Linux faced, and Linux was able to keep pace with competition and gain popularity. Same with systemd adopting machine-id. If they focused on fingerprint resistance, then other core features of modern Linux distros would have lagged behind, and I might not be using Linux today.