What exactly is exploitation, and why is it bad?
If two parties each have something the other wants, and they agree to the transaction, where is the exploitation? If we posit that exploitation exist any time that either party has an advantage over the other, then it becomes true that the only fair trade possible is when both are in exactly equally advantageous positions.
This means no one richer can ever trade with anyone poorer. And the poor stay poor. This is a bizarre result for claims that originate in wanting to make things fairer.
Now, that's not to say that some practices aren't immoral. If someone commits crime... they use violence or threat of violence to compel trade, this is wrong. Use a stronger word than "exploitation" for that though, call it what it is, violently criminal. If someone uses fraud to deceive someone into trade, call that what it is again: criminal, fraudulent.
The gig economy is definitely opportunity. But what sort of opportunity? Likely it is a bad one. It isn't exploitation (I don't think such a thing exists), but that doesn't mean that this sort of work is anything worth taking. Uber, for instance, seems little more than a way to siphon value out of new/newer cars, until they are worn and broken.