Each one has its place and use.

WhatsApp for example, is good for a small group of people. We have one for my immediate family. Two married daughters do not live with us anymore. Two super-busy sons are rarely seen. We communicate and exchange news ..etc. We see our funny grandkids.

However, forums are best for larger groups with different discussion subjects. In my corner of the world, we have a WhatsApp group for people building their houses. We exchange ideas and info. Needless to say the group is chaotic. One guy is asking about the best plumber, the next is showing a contractor mistake, the third is advertising their engineering office. Total mess.

Beautiful thing about a forum is to categorize discussions. One section for plumbing, one section for electric, one section for gov codes and regulations .. etc. Much more organized than all these forms of social media

BUT ...
Most people won't even think of going "back" to forums