> It never really took off though, and even back in its early days it saw barely any use. Over the years it just deteriorated further, and today it's basically completely dead.
It's actually not completely dead... It's just (almost) completely non-public.
You can subscribe to services to get number porting information where the interface is basically e164.arpa/ENUM queries to a private nameserver over a VPN. I don't know the details, the cost was high enough that it didn't make sense for my employer to pursue it.
It's also not uncommon for telecom providers to use it for their own internal routing because enough telecom software did in fact develop support for it despite lack of public implementations.
As someone who's been in the VoIP industry for over 20 years it makes me sad to think of what could have been if both ENUM and IPv6 were more widely adopted. For many years you could reach me via email, SIP, or Jabber with the same identifier and if there were effective support for ENUM in the USA my work phone number would have been able to connect you to any of them, directly and with G.722 HD voice long before it eventually came to modern cellular networks.