To actually answer your question
Is there anything that can be done legally against such companies which exploit candidates?
If you were capable of doing the same thing you would not be applying for an internship, you'd be applying for a job. An internship is for training purposes. They're not exploiting candidates they're just looking to train people or find someone fully trained who is stupid/desperate enough to apply. They don't force you into signing a contract, you can reject it if you're not happy with the pay or the terms. If you have to do the exact same thing as people full time, why don't you apply for the job instead?
Can you do anything legally?
I've noticed companies post lists of requirements for an intern role but they expect them to do everything that would be required by a particular role as an employee from day one.
This is simply not true. This is what you are going to be doing at some point during your internship. Once trained and on the level of where you can do more advanced things it is correct that you may be doing a similar if not exact same thing for less wage.