I never have to debug why my dhcp server isn't handing out ipv4 addresses or deal with conflicts, but if I did, it'd break mdns too. mdns is an extra moving part to deal with.
I've had numerous issues with dhcp servers over the years and clients not understanding their responses. Acting like they never have issues is just burying your head in the sand. mDNS often works just fine on most common OSes, if you don't explicitly block them.
By debugging I mean just checking if you have not blocked broadcast packets at the firewall or some similar misconfiguration. I doubt it’s actual bugs when it doesn’t work. On your second point, it’s actually more resilient than DHCP because it works with IPv6 too.