Forums everywhere are losing traffic. Bear in mind the idea of a forum pre-dates social media. I joined my first forum (Corolland - when I had Corollas!) in 2003, joined CoolRunning in 2007 when I started running. I first joined Facebook in November 2007 and in the ensuing 8 years FB has come along leaps and bounds.
Any web-based platform is only as good as the traffic it generates. A general dating site, for example, wouldn't be particularly useful if it only had 8 guys and 3 ladies, for example. A car forum that has only 2 users a day may not generate timely responses to specific issues.
That being said an advantage of coming to forums like JC is you see alternating points of view. Even though you may not agree with them, you can at least see differing sides to arguments, and see why people think and do the way they think and do. A massive downfall of social media though is you can choose to see only the news and information you want to see. Confirmation bias. It has led to a polarisation on many social issues, with deep extremism developing in the Left and the Right.
Speaking as a high school teacher, Facebook is well and truly still in full use. In schools that have 'Bring Your Own Device' policies and I am conducting lessons that are ICT-based, you must be always circulating to ensure that the kids are doing the work they should be doing, and not what they shouldn't be doing. I know the faint outline of a facebook/instagram/messenger/snapchat page from 10 metres away lol! Many a deputy about the place would be very, very happy to see the back of social media usage in young people.
