People have lots of good ideas that never get shared. How you phrase questions about sensitive topics dramatically changes the substance of the answers you receive. Next time, try couching your questions in non-threatening hypotheticals.
For example, if you ask someone to list areas of improvement for their boss, they'll likely hesitate to share their true feelings because there is no upside to sharing that information. Additionally, they potentially face harsh consequences if their answer ever becomes public.
On the other hand, if you ask what someone would do if they were made the boss with twice the current budget, you'll hear about specific ideas and get a clear picture of what needs attention without the concerns from before.
I like that this is asking what can be done better next time instead of asking what's previously been done poorly.