There is also threads like these every so often from disgruntled members who have seen the slippery slope the forum is on.
But...
While there is truth to your ramblings, this forum would be dead if it were split and/or more closely monitored and censored. It's an ebb and flow, sometimes there is some periods of crap and there are times of technical flow. Sadly, the ebb and flow in here is like watching a beach [of knowledge] get slowly eroded away. But it is the nature of the owners of the cars, they have to put in their thoughts and knowledge.
The thing is, the 240 is the new civic, and the import version of the ford mustang. its cheap, and easy fast. So, therefore it's going to be owned by a younger crowd that for the majority, lives paycheck to paycheck buying parts and spends their money on car parts that might not necessarily do anything. This also entices them to do DIY things, which are often ghetto (I'm guilty here).
The 240sx community as a whole thrived as a base of knowledge between 1999-2003. While there are still breakthroughs and innovations, and people are making more power and doing more badass things, the pool of FAQ style conversation has been done in one form or another. So there is an inevitable stagnance involved, because obviously the majority of us aren't engineers with loads of cash to fab up rom tunes, head packages, and put together motors that make max power at little psi. we're not supra owners, we can't all have 12 second cars with 800hp. we're not suby/evo owners, who can all have badass looking cars that run 14s. we're 240 owners and its exactly like ford mustang owners. there is a percentage that have badass cars, there are some who have primered rust buckets with welded diffs. some have power, some have noise. some are douchebag drivers, some are not. every motorswap known to man has been done now, and power outputs are just raising the bar monthly.
to me, if you don't want to see the junk that is posted, don't read it. its not going to stop, but as the cars get older and newer platforms get older and become more accessible to younger crowds (just think, in 5-10 years, there will be wrx's, evos, 350z's, g35's, and stuff all over the roads with teens driving them - esp judging at how many are sold and out on the streets as is), the 240 will fade into true "old/classic" territory, and will slowly fade out of the limelight into more of an era where the true enthusiasts keep the cars, and quality things like restorations and true hod rod buildups take place (not that they dont now, but not in my budget yet).
ps - i myself have been contemplating new car for months now. its just hard to decide. im on the fence about a new Z. start modding yours and give us some techy shit to drool over.