Unfortunately I would argue that forums are going to go the way of BBS, IRC, ICQ, AIM, etc. in one generation. Hope I am wrong.
IRC/ICQ/AIM aren't really gone, in fact I'd say that sort of application is the most used form of communication there is. If you're familiar with Whatsapp, Facebook Messenger, WeChat, QQ, Skype, Snapchat, Viber, Line, Telegram you'd see the chat space has grown tremendously and you could even include things like Discord, Teams, Slack, etc.
The difference between those I've mentioned and the ones you mentioned? They were stuck in the 90's, no evolution, no vision or investment. I can think of a problem with each one of those:
IRC, you had to connect to servers and check your ports were open and shit just to talk to people, were bound to get kicked out and banned for talking in the wrong place and the irc clients weren't very intuitive. In fact, I cannot stand IRC although it was the foundation for a lot of how we chat online these days.
ICQ, I was a very early user of "I Seek You" and a 'phone number' for the internet made a lot of sense but even with a short(numerically) ICQ number, they were stupid hard to remember and logging in was a pain in the days without password managers. So while I LOVED ICQ and have used it a lot, it was popular because frankly it was the best at one point and become not the best very soon after not to mention AOL bought them.
AIM, obviously many people used this along with MSN Messenger.... a/s/l? The problem with AIM is that AOL was a victim of its own success. They were a Paid service and people were dumping it left and right for hotmail and yahoo mail because they were free and each had their own chat clients. Plus, dial-up really sucked ass so nobody ever had a reason to go back when AOL email went free.
So these services were simply beaten by competitors and not a major change like typewriters to computers.
The internet has one advantage over Facebook that will keep websites and forums alive: Search. The internet search will never go away, it will always be the way to try and find information you do not have or cannot locate otherwise. Facebook has a host of privacy issues and you cannot search anything inside of a closed group(which is virtually every single good group) from the open internet.
Additionally, a forum can be accessed in many ways, from a mobile web browser, desktop or even through a dedicated application...Just like Facebook. The problem, is you are only familiar with old tech forums who have not evolved. Just coming to this site, it should be apparent that getting around is less painful than it is on the old vBulletin forums and many more things are coming which will continue to make the experience not only tolerable, but entertaining and resourceful.