Dragon moves only do super effective to 1 type, don't effect fairy types, and it uses special attack, which kommo-o is lacking. Kommo-o also has a x4 fairy weakness, making any fairy move kill it. Kommo-o is also slow. It also wastes a moveslot because it uses Clanging Scales, which lowers your def if you use it again. Honesty, if it were on a fast special attacker, then yes; but it is not used by one, and therefor isn't great. One of the lesser species-specific Z-moves. At least Kommo-o is in UU(?). Vicini is in OU (or UUBL, IDR), so it seems Z-celebrate can work better..