I spent a few days on each taking in the vibe. 

X is nothing but vitriol and bots. Engagement is just how many people react to your notes. There actually isn't any conversation, just people talking at each other. 

Bluesky is performance theatre. The people seem nice and polite but the notes are just virtue signalling to each other. No one is talking about their real life or anything beyond the superficial. 

Nostr is a odd collection of Bitcoiners, techies, and misfits who hang out on the edges. There is actual conversation and exchanges of ideas. People talk about their day and aspirations.