I was doing things with older people when I was younger. It happens, and I often was the instigator. At the very least, I wasn't saying "no"

But I don't think it's appropriate for older people to go after younger people. Even if I was attracted to younger people, I wouldn't do it because of the power inbalance. It just isn't appropriate, even if both of you are at a party. By virtue of you being an adult, you have more power.