@Uni-the-Unicorn! and
@dave2008
I know the artwork isn't a great guideline for size, but the issue lies also in (again) the design of 5E.
ANY creature that is gargantuan fits in a 20x20 square (ridiculous), because they have no size category larger (like colossal--where did you go?).
Which is precisely the problem.
Why scale damage for every other creature
except dragons? If it is a CR thing due to their system, I agree, change the fricken CR! Or if the damage issue is the problem lower the breath weapons a bit to compensate (since that damage is only guaranteed
once in an encounter really).
In short, any sort of representative scaling would be fine with me, it doesn't have to be 1d10, 2d20, 3d10, 4d10. It could be 2d4, 2d6, 2d8, 2d10 or even 1d6, 1d8, 1d10, 1d12, or whatever, depending on the damage value you think dragons' bites should have by age.
FWIW, I've already decided to house-rule the damages to scale (for bites and claws), and will probably adjust the breath weapons (I mean, seriously, 16d6 for young and 18d6 for adult???).
I just know oftentimes there are errata that has been released I might have missed, and wondered if this one of those things. I hope they "fix" this in 2024...