One can easy see the teen dragons as jerkass and the adults as uncaring of the situation of what they do, but it could be seen as a dragon's way of life. With the teens not being mean to Spike but toughening him up. In real life, most reptiles have little involvement in child-rearing. On the other hoof, Spike may have just chosen the bad crowd when it came to dragons and the teens are just sadistic bullies.
Since phoenixes are immortal, smashing their eggs may be a way to keep their population in check.
Did the dragons accept Spike into their gang because they respect him or did they want to use him as bait for the phoenixes and not give a flying feather on what happened to him?
Moral Event Horizon: The teenage dragons were already giant Jerkasses, but they definitely cross that line during their Dragon Raid. They were willing to attack and eat a bunch of chicks and then urging Spike to smash the left over phoenix egg.
Spike's pet Phoenix, Peewee, was an instant hit with fan art trickling in less than an hour after his debut.
They Wasted a Perfectly Good Plot: A lot of the questions that Spike goes on his quest to answer are ignored. Sure, he decides that some of them aren't important, but it still would be interesting to explore. Four seasons later, the show finally delivered.
In the case of World Building, this episode didn't tell us the point of the migration and finding out that the dragon life cycle has a teenager phase didn't reveal anything unexpected.
Ugly Cute: Crackle, the only dragon named in the show, looks so terrible that it is adorable.