With WiFi, MAC addresses become more of an issue (as you're often scanning and roaming), but we have randomisation algorithms for that.
The same was true for IPv6 for a while, but that too has been solved a long time ago.
For a SLAAC client whose privacy extensions have been disabled for some reason, it's very much possible to figure out your MAC address. This may be a problem on old hardware that doesn't receive updates anymore!
