Many people left because the forum is overrun by spammers.
This is the obvious answer. It's hard to get a decent discussion going here. Either it gets overrun with spammers, or those desperate to gain rank with negligible value posting, or it gets moved to off topic by a mod, and then it falls off the first index page before your mouse can get its clicker out.
Still spammers are here and there in the forum and elsewhere. But otherside there are some helping to take the forum with good value. I see after merit system came in by last January. After that to now.
There is gradual downfall of spammers over the forum. We can ask admin to implement the more regulation act against spammers.