Incenjucar said:
Why should dragons resort to silly mortal structures like spells when they can use more primordial forces?
"Because I want them to."
Really, I think the designers need to take the view that people will do what they want with the game, and they should give us to the tools to do it. What does it matter if
you don't think spellcasting dragons are cool? Someone might disagree with you. D&D should be their game, too.
Don't like rainbow dragons? Awesome, all dragons in your world have logically environment-appropriate coloration. Don't like weak dragons? Awesome, all the dragons in your world are mighty. Don't want complicated spellcasting for dragons? Awesome, none of your dragons have spells and they all just use monster powers.
Like rainbow dragons? Like fighting wyrmlings? Like adding spellcasting? Awesome. Those need to be options, too.
I don't think the 5e team can approach any rules element, including dragons, with the idea that they're telling us how it's going to be. They need to approach it by giving us the tools to make it how we want it.
That kind of conflicts with the typical "alphabetical listing of creatures you might encounter" model of a typical Monster Manual, but honestly I don't think that encyclopedic database is very relevant for the play of the game now. Rather than say "Dragons are too proud to bother with mortal spellcasting, so we didn't design them to do it, and they don't" the game needs to say "Here's how to add class abilities (including spellcasting) to any monster (including dragons), and what happens when you do." I think the 5e MM needs to be more of a challenge-building-book and less of a creature-reference-book.
I've got my view of how dragons in my games should be (powerful forces of nature that dominate the campaign but are also spread out over several levels to make them a reoccurring theme rather than all just distant threats), but my view is just mine, and it shouldn't be forced on anyone who has a different view of things.