honestly i think i would go further and say not only sis they deal with celestials thoughtlessly and carelessly id say the dealt with all outsiders as well as fey and undead really shoddily in a variety of ways and with the exception of fey completely thoughtlessly and carelessly too. (They did think about fey a bit more than the median outsider i think)5E has a huge giant problem with Celestials.
There's a reasonable argument to be made that we don't really need a lot of stats for them, nor do we need the same sort of detail on their society that we might with Devils or Modrons or the like. I'm totally okay with that. But we should have SOME sort of idea of what is supposed to be going on, because it's clearly changed dramatically since previous editions!
For example, 5E made a completely boneheaded and bizarre decision to make it so Good-aligned gods, no matter how dodgily Good or how Chaotic or whatever, have utterly dutiful hard-LG Angels/Celestials serving them (never mind that there's potentially a limit to how dutiful any LG being can be compared to an LN one).
And everyone else, all the N and E gods, even the LN gods (which are very common, and have often had angel-adjacent beings serving them in previous editions), have... NOTHING AND NO-ONE.
No, they do not have devils and demons (not as a matter of course - the books actually go out of their way to point out devils/demons serving evil gods are the exception, not the rule). They don't have anyone else either. Modrons etc. don't seem to be serving Neutral gods either.
It's bizarre. And it seems like someone just put this in without examining the consequences, or how this changes things. And this is seems very representative of how 5E has dealt with Celestials in general - carelessly and thoughtlessly.