Rest assured most people still view the Forums regularly and they are still the central hub of communication for Gaiscioch. That said each person uses the Forums differently. Me personally, I only look through the Recent Discussions sections for post, but I'm a poor example of your average Forum user. The most important thing to consider when posting something for the Gaiscioch family to read is 1: who do you want to reach 2: how fast do you want to reach them.
With the "who do you want to reach" decision always assume that the Forums will reach the entire active Gaiscioch family. I only say that because again Recent Discussions in on the dashboard and everyone sees it if you give a little scroll down. Now if you post in a discord channel you must assume that you will only reach discord users, for obvious reasons. Though I do enjoy discord the text channels do have their flaws. One of the main flaws is they it's very hard to keep a conversation or thought going over any duration of time. there are often several different conversations happening on top of each other (especially in a gaming community the size of GSCH) and it can be hard to follow a single conversation.
With the "how fast do you want to reach them" decision always remember forums reach people only when they check them where as Discord has channel notifications and even sound notifications so the message reaches its audience much faster.
Personally I like to use Discord for announcements and shutouts, while if I have something I'd like to share with the family as a whole I would post in the appropriate forum. For example if I get a wild hair one night to lead a WvW group or something spur of the moment I'll post in Discord. On the other hand If I want to plan something that is maybe a week out, then you're gonna see a post about in on the Forums. This is so the largest amount of people are able to see it, and I have a place for relevant discussions without Kitty breaking it up with a cat picture (Love the cat pics Kitty!!!).
I hope this helps. Also remember with forums you can check the view count if you are ever curious on whether or not what you post is being read. Just because you don't get a reply on a post does not mean it has not been read. It just means no one had anything to add.