I almost never use it to talk to people these days, and typically see one, maybe two other people logged in at any given time, when it used to be a lot more. And I think one of those is someone like me who just has a client always connected. I like what XMPP stands for, but it really does feel like it's faded in at least the "general instant messenger" sense.
I feel it's right that a protocol doesn't need to be in the general consciousness. See the even worse Google trend for SMTP, for example, despite email still being considered a growing network.
I wrote a bit about protocols being for developers and not users at https://snikket.org/blog/products-vs-protocols/
Why didn't you look up Email instead of SMTP? It's not like you want to measure XMPP based on a XEP.
Protocols might not be for (end)users, but the underlying concept is - depending on what you want to build: A product or an open standard.
The protocol is important to users in the sense of devs.
An open standard requires users and devs.
I'm one of the many people actively working on XMPP projects. Is there something in particular that makes you think this?
People often talk about XMPP in the past tense on HN. It's understandable, XMPP had a peak of popularity with the adoption of Google Talk, but Google being Google and shutting that down did not end XMPP. It continues to be active and growing.