Government often tries to do things it doesn't have the power to do. The results of such attempts cause much trouble.
Government can't create any wealth.
The only real sources of wealth are work and energy source production. Government can't do either. Most of the failures of government policies are caused by the assumption that the policies can create wealth, or the failure to use the fact that work is necessary to create wealth in their economic models. Work is necessary to create wealth, because this stupid planet can't feed its human population without humans doing work to produce food.
Government can't create any jobs.
Because government can't create any wealth, nothing government does can create jobs. Instead of creating jobs, the government just moves them, causing more jobs to disappear elsewhere through the taxation needed to "create" the jobs it claims it created.
Note that government can cause lost jobs to reappear by removing the regulations that eliminated them. Government can also create the facility for jobs to appear by providing adequate roads into an area.
Government can't be any size it wants to be.
The size of any government depends on the size of the economy it is imbedded in. If government tries to take too much of the economy away in taxation, the economy shrinks. With even higher taxes, the government shrinks too. The optimum size of government is 10 percent of the economy.
Government can't change people's beliefs.
Government can fool some people into believing something by lying about it often enough, but it can't change the beliefs of people who know what is true. It also can't change religious beliefs.
Government can't control real prices or real wages.
Most wage controls (including the minimum wage) cause inflation and job losses. Most price controls create product shortages and job losses. Farm price supports create product surpluses. Most of these effects end up undoing the original intent of the controls. In the case of wage controls, the inflation so caused undoes the benefits of the controls. Minimum wage and living wage controls do not help the poor, because the inflation so caused raises the prices they pay.
Government can't regulate profit without destroying jobs.
Removing profit removes the reason the business exists. Without profit, business has no reason to hire. If the business does not make enough profit, it must necessarily go out of business. This is because the business can't do necessary upgrades and repairs to stay in business, and because the owners are not paid for their sacrifices to run the business.
Taxation of business does not reduce profit. It increases product prices. When government covets and takes profit away from business, it destroys jobs. Also, excessive taxation and regulation causes businesses to flee the country.
Government can't fund massive social programs.
Because government can't create wealth, government can't fund massive social programs. Attempts to do so drag the economy down through excess taxation. Higher taxes destroy jobs by soaking up the money needed to pay wages. With fewer people working (due to job destruction, and due to social programs attracting people to not work), less wealth is created.
Government can't increase the real wages of workers.
Government can't make the employer pay the worker more than the work the worker does can be sold for. The employer has to sell the products the employee makes to get the money to pay him. There is no other source of money to use to pay the employee. This is an immutable physical law, not a man-made law that can be legislated away. Thus, the entire concept of the "living wage" is a farce in all ways except reducing taxes to a livable level.
Government can't prevent disasters, control the climate, or change the laws of physics.
These are naturally occurring events, and nothing government can do can change them. And because government can't create wealth, government can't pay for the damage resulting from large natural events.
Government can't equalize incomes or help the poor very much.
The ideal of the egalitarians is that every person makes the same amount of money. But it can't work that way. There must be rich entrepreneurs to provide the businesses that create the jobs. And there are some people who refuse to work, or believe that somehow they are entitled to a living because they are alive. These things are beyond the control of government.
The second biggest problem with politicians is that they think that they are all-powerful.