They are just a way for current workers and retirees to give back nothing while claiming they have sacrificed, while public services are destroyed. That's what happened in New York City in the 1970s, after all, despite Tier IV. Just ask an honest actuary writing for Governing Magazine. Two recent reports, he said, show "the obvious need to adjust pension and retirement benefits of current employees as well as new hires — a concept that until now was avoided by politicians across the country and is now a heated topic pending in several courts today." That’s because “the stock market alone cannot save today’s pension funds from the $800 billion in underfunding problems that they have accumulated from overly generous benefits increases, a decade of stock-market underperformance, and employer underfunding. To make matters worse, nearly $2 trillion of liabilities of retiree medical benefits program are almost completely unfunded.”
For his opinion as to what should be done, read the linked article.