I have only been on the Forum since late 2012 (I think you joined the same year, Tom) but I don't feel myself qualified to comment on the reasons for the decline of membership or lack of posting...I'll leave that up to the guys that have been around forever. I can tell you that I'm on the Forum almost every day and I see more and more junk being posted...games, jokes, cartoons, word games, etc. The controversial topics are top of my list for not participating. Long threads covering nothing but opinion are right up there also. Some, I'm sure, have dropped below the radar because of the CNC posts (BTW, I don't agree with that). I have joined other forums and even as a member, I generally lurk until something comes up...that doesn't make me a bad member or it a bad forum...I'm still learning...
I respond mostly to those posts that ask questions that I can answer, welcoming new members and helping to troubleshoot when I can. Having said that, if a question has already been answered I typically don't post anything more in that thread unless it's additive. I assume other members feel the same way...if it's answered, what else is there to add...?
If Stick had posted only one chart and it answered the OP's question, I suspect there would not have been anymore posts anyway. In all honesty, I used to skip over your 17 post but it didn't stop me from participating in the thread...I just didn't read that particular post. Having said that, I copied your 18 post into a document and stored it along with all the others that Stick and others have posted. So I can't say all those efforts that members have put into them has gone by unappreciated. I have a whole library of documents and complete threads by subject just so I can refer to them.
I suspect the old-time members have their own reasons for not participating. Some of it may be that there just isn't anything new to talk about. No thread is started that hasn't already been started. But members, even the oldies, patiently respond to a newcomer anyway. (The Search function "draws a vacuum")
From a newcomer's perspective it is difficult to start threads because many of them just don't know enough yet...other than the problem they may be having or looking for suggestions. I joined a forum a few months ago and I find that as they discuss products and models, I just can't contribute. I contribute where I can but I'm certainly not a super-poster like you old-timers. Besides...us newbies generally become members to learn (the old two ears, one mouth theory)
I also don't bring up certain subjects on this forum because I have learned that it only draws negative comments. For example, I've been using a RAS since about 1980 where I've ripped with it, made tongue and groove in hardwood planks, dado's and grooves and even so far as cutting coves much like has been described here with the table saw. We all make do with what we have.
To what I described above, and your own opinions and observations, I would add that pressuring newcomers to post their pics of their projects, shops and tools is a bit much. Imagine how a newcomer feels while they're starting their projects or tool shopping and we pressure them for pics...knowing they've made mistakes or feeling bad for buying inexpensive tools that they find out about only after they've been on for a bit. Yes, in lots of cases a tool is condemned with no explanation or basis. How do you suppose the new member feels about posting questions related to their tool at that point. On the other hand when a member gets a response that describes poor customer service, parts availability, quality (based on VOE), etc. I'm sure they appreciate it and will not make the same mistake. What about all the bad links that have been posted...or sent to ereplacements.com only to find their tool is not there...? Haven't you also noticed how many times an answer is just plain wrong...?
Members will come and go...others will not do as much woodworking as in the past, newcomers might feel they don't have anything to add, some will be scared to post their projects because they might believe they don't stand up to others that have been posted...lots of reasons...
I would suggest that you Forum Contributors pool your thoughts and come up with the top reasons people might not participate and put them in the form of a poll vote. Then you guys can get together and do something about "the winners"... Assuming something needs to be done..."do nothing" is always an option and sometimes it's the best option.
Just thinkin' out loud...not at all presuming I have a better opinion than anyone else...just trying to be additive.