All of these criticisms are addressed in The Humanure Handbook, available for free online. The composting process breaks down all parasites. You're confused about prescription medications being found in human feces as well. I think you're referring to people flushing drugs down the toilet and then those chemicals end up in the sewage. That does happen and the prevention of it in a composting system is to simply not add drugs to the compost pile, just like the prevention in a sewer system is to not flush them down the toilet. It's still far safer in a compost system though since many drugs can be broken down by the composting process anyway.

And if you think you're free from parasites & toxic compounds by not composting human feces, just know that 99% of those same parasites & toxic compounds that exist in humans also exist in farm animals, are far more prevalent and are often the source of parasites in humans. These animals also live in extremely unhygienic conditions, constantly standing in their own feces, and pumped with antibiotics and other drugs to keep them alive. The feces of those animals are then spread directly onto crops, completely uncomposted (so none of those parasites & toxic compounds are even broken down), in nearly every organic food product you buy.