Pension plans may not be able to get better returns, but they can specifically balance their assets and liabilities better by picking specific investments and/or buying/operating private companies.
An index fund will underdiversify by only selecting public companies, and over-represent companies with short-term interests (the total opposite of a pension plan!).
The underdiversification or index funds is a particular issue ex-US where stock markets only represent a few sectors.
Pension plans can sure screw up, but they can also be unbeatable.
They all have short term interests, since the people doing the investing aren’t going to be around for the whole ride. In theory, defined benefit pensions are great, but in practice I haven’t seen any evidence that they have sufficiently superior performance to make up for the possibilities of bad investments, corruption, etc.
That is atypical from what I see in the US. In the US, if the pension fund is doing well, that means the politicians offer the government employees unions better benefits, and so all the union members vote for them and since not enough other taxpayers vote against them, we just end up with inflated benefits.
An index fund will underdiversify by only selecting public companies, and over-represent companies with short-term interests (the total opposite of a pension plan!).
The underdiversification or index funds is a particular issue ex-US where stock markets only represent a few sectors.
Pension plans can sure screw up, but they can also be unbeatable.