In this case, where it's literally "Here's an image, all you need to do is tweet it," I'll accept that. Its very minimal work, for minimal exposure. No real foul play there.
But I completely contest that folks like influencers can be paid for real work through exposure. If instead someone like Ginny D was asked, "Hey, make a well-edited video talking about our upcoming book, its gotta be really funny like your normal vids. We'll retweet it as your payment, think of the exposure!" That's real time and effort they put into stuff like that. If you want someone to shill for it, you should pay for it like any advertiser would.