Most of these sites are spam, scam and malware. Especially in tlds like .xyz that give/gave free/$1 domains.
Quality ngtld sites and alexa top million are two completely different things right now(and will be until registries stop offering free/$1 domains).
IMO, the real and actual growth of ngtlds can only been seen by tracking registries that follow a stable pricing strategy above $15 per domain like donuts that mainly attracts end users and not spammers.
I'm not saying that there aren't quality sites on tlds like .xyz but most are not. As a matter of fact here are the top 50 .xyz sites according to alexa rank. Except for abc.xyz I haven't visited any of the other sites but I think it's obvious from the domains that these aren't "end user" sites.