Poor pay, poor conditions and a crap work force. Bureaucracy and lack of autonomy. Virtually no ability for a department to adapt to it's workload.
I've worked in private and public sectors and whilst private sector has its stresses you can move company and know it is likely to be different. Private businesses can get rid of crap employees who don't pull their weight. Decent private companies will expand and collapse their work force to meet demand. In public sector, particularly healthcare and statutory services, if you have 50% of your workforce they still have to do 100% of the work otherwise people die. You end up with serious burnout because of it.
I'm talking like for like roles e.g. both need a genetic degree and x years experience or both roles are admin. Not talking private Dr Vs NHS Dr etc.
For example, I work out of a dilapidated building with currently no working toilets and limited running water. We pay for our own tea, coffee, mugs, milk, cutlery and bought our own kettle and fridge. I'm a project manager and on around £40k, so not a bad salary, but I'm doing 2.5 people's jobs and working the hours to evidence that. We get maybe 1 or 2 applicants per job, and they are usually lacking experience or not qualified for the job. I wanted to make a difference, I wanted to be part of the solution to societies ills so took a public sector role. We offer no incentives to get people to stay when they leave despite knowing we can't recruit to fill them, there's no negotiation on salary, there's no benefits beyond the pension and sick pay.
My old job - same salary, fancy city centre office with cleaner, free tea and coffee and filtered water on tap, negotiable pay rises based on performance. There were times I worked waaay over my hours but when it became evident my role had grown to more than one person's ability, we recruited. When we didn't get suitable applicants we increased the starting salary and benefits package and offered better pensions and maternity packages. When staff handed in notice if we felt they were good we would offer incentives to stay. We valued the work force.
The NHS and most public sector is essentially operating like a minimum wage business and expecting excellence. It's not going to happen.
I'm going back to private sector!