Prices go up and down. A lot of the high prices has got to do with the fact that those who had these consoles as kids are now adults with steady incomes. Right now it seems to be that everything from the NES to the PS1 is what is currently getting inflated, while systems both older and newer than those are much cheaper. At least that's how I see it. Of course there are other factors as well, but I believe this is a big part of it.

Another factor is that game collecting has become a more widespread phenomenon, and therefore there is more competition driving the prices up.

At the same time, even games from the NES and SNES are generally lower priced than if you were to buy used games back when the systems were new.

As for boards and sites about classic systems and games, there are a couple of things to take into account: The amount of information on classic systems and games available has increased tremendously during the last decade. It is also much easier to find. People don't have to ask for help on boards to find out how to get to the next part of Super Metroid when they can just look up a walkthrough or a Let's Play video that explains it or shows how. People don't need ask others to find out what games are the ones to get for their older systems, because there are already tons of lists and videos about top games and hidden gems, etc.

In addition to that, people who are extra interested in a certain system often ends up on "specialist" sites. So a lot of the "traffic" that you were used to might also just have moved somewhere else.

I would also like to point out that "classic gaming" is a very vague and relative term. To some people, Atari 2600 is "classic gaming," while PS1 is "modern gaming." Another person might call the PS2 "classic gaming."

And in the end, the world around us is constantly changing. The society is constantly changing. Our lives are constantly changing. Technology, economy, politics ... And our world view is constantly changing. I think it would be very, very strange if something as small as "classic gaming" wouldn't. In fact, I'd say it has been changing the whole time. And it's certainly not just bad things about that.