Personally, I think Discord is super handy for just socializing and having game related sub channels that can be kept separate from spam or off topic banter. It also is great for tagging people you need to talk to about the RP, get collabs rolling, and pinning messages.

That said, not everyone has Discord and as others have mentioned, stuff gets buried if the chat is busy. I think GM related announcements and inportant info should always be posted OOC, or just general player updates and remarks. A balance of both is good. I just think it's silly to discount a tool entirely because it takes attention off site.