So you don’t have any criticisms of that encounter? It’s perfectly designed?
No, and no. I hardly expected perfection. But, for what it's clearly intended to be - a challenge where 'success' is having the courage to go out and get beaten down in spite of being pretty sure you have no chance - it's not that bad, nor do I see how, given the format & the system, it could be vastly better.
One aspect that I'll agree is lame is the note that Cyanwrath will be replaced by another half-dragon with identical stats on the off chance he is killed. Either his absence should have been notable later, or his 'replacement' should have been decidedly different, or both.
I agree that death is and should be part of the D&D gaming experience. However, 'Greenest in Flames' is an awful introduction for new players to the game (likely in an Encounters setting). The entire episode is a meat-grinder (numerous unbalanced encounters with no resting), it has an encounter with a blue dragon that must be played in an illogical way in order to not kill the entire party
I'm more with you on these points. While the structure of Greenest in Flames does a pretty good job of pacing a 'day' (actually night) the way it's apparently supposed to be in 5e (the encounter guidelines suggest a 6-8 encounter day, and at least imply 2 short rests, and, for first level, give a target of 300 exp per player, enough to level up). Each of the hours of the night available to them, the party can either accept a mission or take a short rest, declining a mission has consequences, so there's both the opportunity to rest when you really need it (and you will) and an impetus to take on challenges, instead. The major problem is that many of the encounters (and some missions, particularly Seek the Keep can include several) are hard-deadly, even random encounters tend to be hard. For a 2nd or even 3rd level party, it'd've been fine. For a first, TPKs or just giving up and declining all further missions at some point and not making 2nd, are pretty likely results. And, no, that's not a great introduction.
And, yes, the blue dragon isn't handled well. If it's not really committed to the fight and just using it's fear aura, then have the Dragon swoop in the midst of another mission (one that's going 'too easily,' if one ever does) and let them make their WIS saves. The idea that the archers on the wall can't harm it is at odds with Bounded Accuracy, and the idea that it'll keep blasting said guards instead of the PCs who, presumably, do put a little damage on it is absurd - and if it doesn't do that, dead PCs. It really feels like it was designed for a different edition. Bounded Accuracy means that massed fire from the defenders - guards as well as PCs - should have been able to hurt the dragon.