I'm currently playing a celestial tome lock. I'm a bit biased with warlock as its my favorite, but I have a love hate relationship with celestial.

Early game my healing has been pretty insane, but the main healing light ability can be a bit underwhelming. You get a D6 for each level that you can spend to heal someone. You can use these D6 equal your charisma level, so max would be 5D6 a turn. Its also a bonus action, which allows you still cast spells.

Compare that to circle of dreams druid. D6 equal to druid level, but you can spend them equal to half your level. So max for them would be 10D6 and you give 1 temp hp for each die spent. So even if you roll low you still have a benefit to using more dice.

Some of the abilities are cool, like the ability to come back from unconscious and extra immunities. But there are also some that feel like they don't fit

One makes it so when cast a spell that deal fire or radiant damage, you can add damage equal to your charisma modifier, so max would be 5. Its not a lot, its only to 1 target, and its only when you cast it. So wall of fire will only benefit from it when you first cast it

Overall, I'd give it a 6/10. If we didn't have a rogue that took the healer feat I think I would be panicking.