Plenty of unemployable PhDs here Australia. I know one who is tutoring high school students to earn a living. His thesis was on phycology and the production of sustainable fuels. A nuclear physicist with a PhD is unemployable and is retraining as a data scientist. Another phycologist is retraining as a counsellor. A molecular biologist is running a plant shop. The first phycologist is charming but a century ago, he would have been a charming but very average greenkeeper or a gardener.

Bright people in Australia head into finance, medicine or law not into dead end PhDs. The problem is that universities sucker too many into PhD programs for the sake of the departmental government funding. This leads to indiscriminate entry into virtually all the PhD programs in Australia. When they graduate they are often underemployed or unemployed.

The ultimate harm to society is the production of research slop that worsens the SN ratio in published work.

The university pipeline seems to me totally broken as a way to gain employment. It's still effective for prestige. You should stay in school as long as you're still climbing the world university rankings, but once you start falling down this ladder leave and join industry. You will get paid more and do more interesting and valuable work.