Back with D&D3e came out, I was an active participant. Back then, I accessed them through an NNTP client instead of through the web site. (I still think NNTP worked better for such things than web sites.)
When I went “back to basics” with RPGs, I often spent time in their out-of-print forum. My “I used to think...” page was originally a post there.
They tried to turn it into a social network called Gleemax in 2007, which seemed poorly executed and was shutdown by 2009.
By the time D&D5e was in the works, I could still log in to comment on articles posted on their site but got an error when trying to log into to the fora.
I certainly spent more time on Dragonsfoot, ENWorld, and various other RPG-related fora; but the Wizards’ fora were always a fixture of that landscape. I spend almost no time on such fora today. Mainly because I’ve chosen to spend that time other—though not necessarily better—ways. So, I can’t really say whether this is a good decision or a bad one.