We have a lot of abilities that trigger extra damage against chaos daemons but it doesn’t feel like I get to use them much. Are people just now playing real daemons? It seems like everything is chaos but nothing is a daemon.
Daemons see a lot of play in every Chaos gods faction I'm pretty sure. Tzeentch and Nurgle are probably the two where you see them the most, Khorne sometimes focus more on the Bloodbound mortals and I think Slaanesh can be a mix too. Keep in mind that sometimes, unit may not look like daemons but they do have the Daemon Keyword on their warscrolls! Best example are any units that are mounted on discs in a Tzeentch army! That disc is actually a daemon and their warscroll has the Daemon keyword! When I play against a Chaos army, I usually make sure before the game starts that I know every daemon unit on the table, asking my opponent if I'm not sure!
I got to use it against some Slaanesh daemons at adepticon. I agree nurgle and tzeentch are probably more common than khorne in AoS, but I expect there will be more slaanesh players soon assuming next year is the year of slaanesh.