Never been to York, it usually seems to happen when I am slammed at work and can't take off..maybe in the fall. Others have posted about the things that may be causing York to shrink, the fact that the baby boom is tailing off (I am among the younger members of it, and I am in my middle 50's), the 'next generation' if it does come hasn't shown up yet (think about what 3 rail was like in the 70's and 80's, when Baby Boomers hadn't quite come back into the fold yet)) likely looms large...but there are other things to think about. For one thing, we have just come off a bomb cyclone in the midwest, that may have affected people's ability to travel to York, between snow and flooding it was pretty bad from what I hear. Other factors may be involved, it could be some people decided not to go, unsure about economics, personal or otherwise.
The other thing to keep in mind is the social aspects of York, that was once the province only of the TCA, itself a kind of social organization. Back in the good old days, the TCA and York was a major social hub for people into trains, an excuse to meet people from all over and complain and gripe about how expensive trains are, how no one wants to work on the club layouts, etc *lol*. Seriously, it served that need (and likely still does), but that world has been replaced in part by things like this forum, facebook groups and so forth. Whether that is good or bad is moot, but it is a reality, it is just a lot easier and cheaper to do it online then going in person. Manufacturers also likely are cutting back on costs, among other things from everything I have been reading the cost of doing business in China has increased a lot and may be cutting into profit margins, even with price increases, and almost no company is not expense wary these days.
I myself look forward to getting to York, even if it isn't as good as 'the old days'. It reminds me of a story a broadway actress told in her memoirs, she had gone to see the broadway production of 'Man of La Mancha' after Richard Kiley had left, and she mentioned to a friend how blown away she was by the production, loved it, and her friend said "Yeah, but you shoulda seen it when Richard Kiley was in it"; as good as it may have been in the old days, how much might be missing, it still will be nice to go and experience it, even if the current cast isn't quite as good.
It is funny, I was at the Spring Thaw meet in Allentown this year, never having been there (and discovered a really good Hungarian restaurant in a nearby town), and was pretty blown away, and one long time participant told me "this is nothing", if that was nothing, in some ways I am glad I wasn't there in the old days, might have caused me to faint *lol*.