I think pne of the fundamental difference is who is in charge of the moderation.

As bluesky (and any centralized platform) scales, more people show up with a wider and wider spectrum of tolerance. Because of this, more rules have to be made to satisfy the easily offended etc. You play to the lowest common denominator since you can only cast a single net that applies to all. But this eventually results in so many restrictions that most users will feel boxed in. This breeds resentment and toxicity.

Nostr sidesteps all of this. You alone are in charge of the moderation and your moderation decisions affect you and only you. The most sensitive and easily offended person can moderate their feed to the Nth degree while still allowing the most bigoted person in the world to shout their racism into the void. All parties get what they want. This breeds contentment and happiness.