I've noticed this, too. Things seemed to peak in the early 2000's with what I'd call bonafide "excitement." Now you can't even get more than four people to list their Top 10! But it's probably like this with other art forms as well, or styles of music. Take heavy metal and "alternative" rock, which peaked in the 80's. With ambient, which I'd say really "peaked" in the mid-90's, there might be waning interest due to the simple passage of time, or due to the proliferation of ambient over the Internet and somewhat oversaturation of releases.