But humans use their free will to do fucked up shit like building paper factories next to populated areas or dumping their industrial waste into the local water supply. Or smoking around children. No one claimed that the consequences of free will are limited to impacting only the acting agent.
Maybe cancer still existed before industry, but there's no way to deny that industry has drastically increased cancer rates.
I'm not here arguing for theism, but someone said the problem of evil hasn't been solved, so I merely pointed out that free will is a viable answer to about 99% of that problem, and thinkers have been discussing it since at least the Middle Ages, so it's kinda revisionist to say no one has ever answered it.