the new dragon arts are amazing and this one is no exception.

for stats this one got +2 initiative and 13 hp but he lost his con and cha save too. why the hate for lil  dragons :(

he can make two attacks now which is amazing and his breath attack does 1 average dmg less.

overall nice little changes.

Wonder why no age ranges supplied for each dragon type? 

Possibly to grant the DM full reign over that for their world building?

Dragons live for thousands of years if they don't come to an unnatural end. However, notice there aren't any statblocks for Elderly Dragons that are weaker than their younger counterparts? This is because true dragons get stronger the older they get. There is also no official notes on how dragons die. Perhaps to get to dragon heaven the dragon needs to acquire a certain horde value, before then going through a certain ritual to pass on the afterlife? Perhaps they all go a dragon graveyard where their bodies remain as they pass onto another life? There is more mystery in the unknown, and without specifiy these certain requirements you can make these rules up as you go without the players going, "but this book says it's this!"

You can always look to older edition books to fill in these blanks if you want some guidance, but personally for something as magical and magnificent as a dragon, the mystery is part of the wonder.

Well yeah, except the DM needs to know at what point they go up from wyrmling to young, right? 

I mean the DM can just pick and choose. But if you want the official ages dragons ascend to a new age category a quick google search will provide you with what you need. Based on what they printed in Fizbans, it's still roughly the same as what you'll find in the Forgotten Realms Wiki. They only specify the starting ages of Adult and Ancient in Fizbans, which matches the table you'll find here:

https://forgottenrealms.fandom.com/wiki/Dragon_aging

• Wyrmling: 0 - 5 Years
• Young: 6 - 100 Years
• Adult: 101 - 800 Years
• Ancient: 801 - 1,200 Years
• Greatwym: 1,201+

I personally extend the point they ascend to ancient and greatwyrms in my own worlds.