I wouldn't worry about it too much, Ida. I think that younger
men are often just less expressive in the general sense (no offense
intended to any younger men that might read this). It may be
that the only way to know if a younger man likes something is to ask
Another possible explanation is that younger men may be simply indifferent on the issue. I know when I was younger, I was just happy to be in contact with a vagina, ANY vagina. It wasn't until I got older and began to develop personal tastes that I found my unique loves, proclivities, perversions, etc.
I personally think a great solution to your "problem" would be to start pursuing older guys. Yeah, I like that idea... ;)