In short I think it's because of the progression in our society.
Look at the path that quality of car audio has followed since, let's say, the mid 90s. There was a strive for perfection. Constant progression. Innovation. At some point, the focus of high end features and quality was shifted into what it is today. Someone made mention earlier in this thread that no one is dropping money on high end units anymore. Well, it's not a priority to majority of the car audio market consumers. Not to mention, due to the lack of large demand, there really isn't a whole lot of options for us anymore. I'm not saying there isn't quality out there. There will always be a quality option, but the niche that we are (audio enthusiasts) have went from small to microscopic. Large companies have little incentive to cater to a group such as us.
So when we look at big name brands from years back...Rockford..MTX...Kicker...Alpine.. What direction have they taken in the past decade? Rockford? Who misses the old Punch amps? MTX used to be highly respected and now...well..., Kicker? Their path really changed when the solobarics went square. Alpine? Where are the units like the 9835? For heaven's sake, they hardly have an HU worth looking at. Image Dynamics sold out, US Amps shifted, CDT went over seas and cheap.
To some degree, pretty much any "known" brand (read: walk into a brick and mortar store) has taken a slide downward. Well, I'd say JL hasn't but they really haven't done anything innovative since the W7 and that was what, 11 years ago? An entire decade?
As the demand changed, the supply changed, which was following the majority in the first place, as we are in the information age, our member bases will change, so on and so forth. It's a chain reaction. I think forums have declined a bit since other channels of communication have increased a bit, Facebook, Youtube, etc. Picked up a car audio magazine recently? Cared about anything in it?
I don't think amount of interest has changed; it's simply the emphasis of where the interest is. You honestly really honed in on a key separation in that post: "I still use the search function before asking a question."
On a different forum just yesterday, a user was asking about which batteries to cram into the rear of his Sorento. I suggested that he get a sufficient sized alternator and fix the problem. He claimed there were no high output alternators available for a 2003 Kia Sorento. 7 seconds of Google later, my first result yielded a 180amp alternator for a 2003 Sorento by searching "high output alternator sorento". The user then commenced his rejoice of being able to tell his Sorento forum buddies that there was an alternator for them. They had "multiple 10+ page threads" about how no one could find one. No one could find one. No one could Google the most obvious search criteria, but they could drone on for pages about it. We live in the "information age" and have the world at our fingertips, but simply choose to not accept it. It's pure laziness.
So why do I think forums have went downhill? Society has.
