[cweill]

Just ignore them. On social media, ignoring a stranger is not rude. It's the default. And a perfectly valid strategy for dealing with the volume of people asking for your valuable time.

Obviously, when it's someone you know or important to you, give them the courtesy of a polite decline or say you're very busy and will let them know if anything changes in the future. But for strangers: ignore if you don't want to interact.