Maybe they can work well with proper oversight, but the status quo for the majority of defined benefit plans is to be mismanaged and underfunded. See the role (union negotiated) defined benefit plans had in the US auto industry collapse. 60 out of the 100 largest corporate defined benefit plans in the US are underfunded, more than half! Chart in that article shows that 40% being funded is actually unusually high, historical trend is 15-20% of plans meeting funding levels. https://www.wsj.com/articles/companies-u-s-pension-plans-are...
Funding a defined benefit plan for lower wage workers vs paying lower wage workers more and contributing more to a defined contribution plan has exactly the same costs on the employer side. The only way the defined benefit plan appears to work out better for both parties is because we have legalized the employer not funding these plans to the appropriate level and hanging the supposed beneficiaries of the plan out to dry when it goes south.
Even ignoring the rampant underfunding issues defined benefit plans are a classic example of the principle agent problem where the interests/risk appetite of the fund manager and the fund members don't line up perfectly.