Can't you imagine lots of differents effect on the gameplay ?
Specific skills or spells ?
Specific side quest or way to resolve some of them ?
Specific interractions/reactions, gifts, support on your story ?
I don't know... I'm not the best to say what is D&D lore but you can imagine many things...
I personnaly don't care about deity but I can't imagine someone is "against" the concept in a ROLE PLAYING game.
It looks role play and story telling is not intterressants for the "modern" consumers.
Was this a reply to my post by any chance?
It was, I only forgot to consider the "I'm not against" according to the "it really makes no differences"
Maybe I had said another sentence than " I can't imagine someone is "against"", but the meanings is the same.
Alright fair enough.
I don't think a deity for a class that is not forced to pick one would add any spells. I might be totally unaware of some 5e rules that states it does.
All for side quests or way to resolve some of them, specific interactions/reactions, gifts, support on your story would be awesome.
However, there are like 35 gods. Would it be cool to just add 5 and have some kind of MEANINGFUL effect? Like a side quest that isn't just a fetch, more than one line of dialogue in one conversation, a gift that's not just vendor trash or an npc that is just going to be with you for 5 minutes...
But limiting the deity choice would piss "someone" off, so I think there would be a call to have all choices.
So, sure we get all choices. But we won't get a meaning interaction with most of them. This will piss "someone" off also.
So the next logical step would be to not have any interaction from the chosen deity really, unless it is very story specific. I would obviously only choose the deities that added to the story in this case.
Or you could leave it out and let people pretend they followed one deity more than others. And let them make active choices in possible quests to aid or hinder or ignore any deity. This way you act out your belief instead of having it as a tag.
So it's:
1. Have a choice with little or no effect
2. Have very few choices with some effect
3. Don't make an actual choice, but choose as you go along.
And please don't attack people "role-playing and story telling", you have idea what experience or preferences people have.
I have been role-playing, mostly as a GM, for more than 35 years over more systems than I can even remember. I even role-play in computer games.