It might be a small part of a bigger thing.
Snooker was biggest in Britain in the 80's after that we got Ronnie/Higgins/Williams. Since then snooker doesn't make the headlines anymore unless your Ronnie (Every year around the world's we get one of those articles saying snooker is dead), so the sport get's less exposure and less kid's know about it. If kid's don't know about it they're not just going to pick it up and less chance of finding the freakishly talented.
There aren't as many snooker clubs or places with tables around anymore, so the sport might not be as accessible as it once was. With football all you need is a football and you can have a kick about anywhere, if you can't get to somewhere with a snooker table easily you can't put practice in.
Snookers one of the trickiest games with little immediate gratification. To continue the football comparison anyone can score goals playing with their mates and have fun, in snooker no ones going to be knocking in tons accidentally, the first time you'll play you're not going to pot every ball consistently or be able to build a break. It can be a lot more frustrating when you first start playing than other sports.
There's also the thing I'm most worried about which is people love to watch snooker so they have the attention span for matches that drag on but we're at a point where people enjoy watching more than playing or a satisfied just to watch without ever feeling the need to have a go. I'm mainly thinking of Germany the German Masters has great crowds supporting every match but there are hardly any snooker clubs in Germany. If there aren't enough playing the standards just going to creep down.
That went on longer than I thought
but these are what I think are some contributing factors to the decrease in strong young talent.