IMO.... I was a very active member of a few forums, even being part of the team that ran the old Cape Town Fishing and Vas Pappa sites. There were various reasons they all had a decline in attendance, but the biggest reason I found was that there are a few unscrupulous "anglers" who would come onto the sites, see what is happening and where, then go off and notify their other unscrupulous buddies via social media and then just go and wipe out any fish that happened to be in those areas. Don't get me wrong, there are many caring anglers out there who just want to show off what they caught (and these days, who can blame them with all the bad news going around somebody wants to share some good news now and then) but in the end they are not posting these images now so that they can protect "their" local waters and stocks.
There are many other reasons for lack of action on the sites, including those listed earlier, but that was the biggest reason I saw.