The Mirrorball Man
Aventurier
In my opinion, "Divine Magic" is magic granted by a sentient being. The licence can be revoked at any time. That's the only difference with Arcane Magic and it's very easy to implement.
One thing I dislike about 5E is the blurring between these two magic types. There used to be a certain amount of Niche Protection. There was a clear way arcane and divine powers were not only used but gained.
Divine Magic came from the Gods or Godlike forces and you had to have faith to use it.. Arcane magic came from the universe itself and you learned how to use it.
Now it's all mixed up. Some arcane users also can just cast divine magic spells exactly like arcane magic spells and some Divine Casters can just cast arcane magic spells the exact same way as Divine spells.
At the same time many of the casters are exactly like it was before. There is no longer any internal D&D world reasoning for anything. It's just all because. Sorcerers can just resurrect and heal the same as clerics and some clerics are throw around fireballs left and right.
If a bard casts a healing spell with no faith and no other power behind it..why can't a Wizard?
In 5e the difference is the spell lists. Sadly, sort of, its not more differentiated than that. I get why that was the design philosophy, but Divine magic especially I think suffers from a flavor standpoint when it doesn't feel any different than arcane magic other than the spell descriptions.
I have a lot of fun in my campaign with the fact that according to every analysis by sage and scholar bardic magic shouldn't work, and yet it does. Like Tolkien's Tom Bombadil, they're friendly, singing reminders that the world is bigger and more mysterious than we can wrap our minds around.For every class it is very clear why they have spells, except the Ranger, and maybe also the Bard is partially shrouded in mystery. If the mystery bothers you, fill the blanks and figure out where do the Bardic spells come from in your own fantasy world.
Is it a little cheesey? Sure. I still love it though.
We were talking about spell casting, not classes right? I didn't read the OP so I may have jumped in wrong. From a casting standpoint, there's essentially no differentiation outside of prep and rituals, which aren't enough to make things feel any different. My own taste would be to have Divine casters actually feel different in the actual casting. Specifically, their god should matter, and it really doesn't. I completely get the design impetus there, I just don't like the same-y feel of it. The kind of spells, and specific spells, are indeed different, but I think that's a weak place to differentiate. Just a flavor thing for me, it doesn't prevent me playing and liking 5e at all.