There are still a good many users on from the 'old-days' as you say. There are also still several network(s) in which are gaining in user(s) instead of declining in users.
DALnet gets around 15,000 at peaks now, however, I do know that the channel #Toronto there is usually quite busy. The channel #Canada there is also pretty well populated.
As for Undernet, EFnet, etc - I'm not sure about them.
Networks such as Freenode are growing in numbers; they just hit a milestone for their network and reached over 70,000 connections.
Though a lot of people have went to facebook, some of us from the 1996 era are still around. I still prefer DALnet after all these years. The network in which I was a CSOp for 8 years was Webchat, I can tell you they however are on the decline, as well as other networks. You just have to search, you'll find a channel &/or network in which you like.
