I get both the opposite and the same. I'm 50. My sons' pals (we're talking 25-35) hit on me. And apparently, I am the hottest thing since fire for the over 70 crowd (yeah, I know, jealous, right, LOL). The short answer to too young or too old is yes. However, when they ask, they know, they want to bring you into the debate, the power struggle, so they can have a chance to talk you around.
Bad idea and it doesn't work. More men have talked themselves out of dates than ever have talked themselves into them.
All that said, you owe nobody an explanation. "No thank you, I'm not interested," covers it and ends the conversation.