To me the metallics are just unnecessary and aesthetically unappealing duplication of chromatics. They are borne out of the silly alignment system as you needed good and evil version of each dragon, and once you get rid of that, you can also get rid of the metallics as the better looking chromatics can now have any morality. Though one setting I had metallics and chromatics with matching breath weapons to to actually be two genders of the same dragon species.
Whereas I find metallic dragons far more aesthetically appealing (especially if you change "brass" and "bronze" dragons to something like cobalt and iron, so that there's far more color variety). White (beaky and brutish) and black (
literally skeleton faces) dragons both look quite
ugly to me, and blue and green are sorely dependent on artist (
sometimes they look fine, and
sometimes they look butt-ugly). Only reds are consistently impressive. Conversely, I don't think any of the metallic dragons looks ugly.
I also don't--at all--see metallic dragons as "borne out of the silly alignment system." Even if there weren't chromatic dragons at all, metallic dragons still have value as Big Good types, something that is
sorely lacking in nice, ready-to-hand archetypes for people to draw on. (Literally the only other classic Big Goods are
God Himself, Santa Claus, the Good General, and the Good King/Judge/Officer/[insert official authority figure here].) The personalities of the chromatics,
even in the absence of alignment, wouldn't ever be able to mesh with that role. All chromatics are
cruel. They are literally an embodiment of the worst excesses of the rich and powerful, capricious, rapacious, often brutish, always haughty. Metallic dragons are an embodiment of the rich and powerful at their
best, sharing, building others up, hoarding knowledge and beauty rather than crass wealth (hence my special love of gold dragons), dedicating themselves to tackling the worst of life's problems.
Trying to have both of these things embodied in the exact same dragons just makes the whole thing a muddy, incoherent mess. Which, yes, is much more like real life, but we don't generally tell fantastical stories of heroism and bravery and desperate last stands that are set in the real world. We set them in fantasy for a reason: to
inspire. We set them there in the hope that the child who has absorbed these sentiments throughout their life becomes the adult who tries to make the real world just a little bit more like the fantasy in the few moments where they have such a choice.