It’s a market “cheat”. Exploitation is a false premise, the real issue is a surplus and artificial pricing of labor. Nobody makes you take a salaried job, and your free to go at any time.
No one deserves or is owed a job. When you enter a salaried position you’ve essentially contracted for your skill set. If your skill set is needed badly enough then for the “lousy hours” you should either get more or have it in writing you won’t be working 60+ hours a week. An employers acceptance of that means you’re needed bad enough, refusal means there’s plenty more where you came from.
Oversimplify all you want; it cost the Republicans many voters (and two presidential elections to a complete nothing loser). The fact is that while all you point out may be true, Americans can’t earn a fair wage with employers skirting laws to bring in foreigners to replace them for less. FWIW, I haven’t worked a lick of “unpaid overtime” in over five years in a decent job - but it isn’t because my boss doesn’t want or expect it. I’m only able to do that because his pets work even less than a standard workweek and it is done openly. Nobody could ask me to work an extra minute with a straight face, and it is on me to protect my job by protecting my knowledge (because nobody owes me a job and I’m not owed one). If it makes financial sense to pay me, they will (and they do).