I do think that is has gotten much duller around here compared to when I first joined. Personally I blame the splitting up of the forum into overly-specific sections. When I started there only like 5 or so sections: GD, Help Center, TTT, (I can't remember if OT was around when I started or if it came later), KinIME was up in the main group if I recall, and one or two others. Now there are 9 in the main section plus the 3 "Hosted Communities."
The forums has been divided up too much. It used to be most everything went into GD, so you would get a much higher concentration of people and thusly a higher concentration of interesting threads. Yah you would also get a lot more dumb or uninteresting threads as well, but it wasn't hard to distinguish between the interesting stuff and the crap. Now everything is so divided up and spread out that finding interesting stuff means searching through 5 different sections, and few people want to take the time to do that (I know I don't), especially if they're only taking a few minutes on their lunch break to skim through the forum.
I know the idea was to make things more organized so it would be easier for people to find topics that interest them, but it seems to have had the opposite affect.
It also seems that the number of totally random threads has dropped because when people start them they tend to get yelled at for post whoring. Some of those random post whore threads were the most fun ones. It's case of trying to over engineer everything. The fun semi-chaose has been given up for dull pseudo-order.