The Celestial Warlock is underrated.

I do not think its reputation is helped by having such an underwhelming 6th level feature, but by the time you get to 6th level you essentially have 7 free uses of healing word, very useful for getting allies up from being unconscious. It would also be useful for a 2-level multiclass dip, because I can't see any charisma based character being unhappy with 3 uses of bonus action heals

I also think the spell list good, some really key utility spells only a short rest away.

I'm not comparing it to the best of the best, like Hexblade or Genie, but I also think it's a perfectly great subclass.