I believe the root of the problem is creating more money via institutions that don't need it. It would do a whole lot more good to give it to people who do need it and will therefore spend it. Their spending creates profitable business opportunities for others.
People and institutions that already have plenty of money are "hoarding cash" (and real estate) because, after other needs are taken care of, what remains is a concern about security if something unexpected happens. They don't see profitable investment opportunities worth the risk.
Unfortunately, central banks don't have much leeway in choosing where the money goes. Government budgets can distribute money to people through welfare, jobs programs or infrastructure investment. By creating a low interest rate, the central banks are essentially begging governments to take the free money and use it to stimulate the economy. Austerity proponents, deficit hawks and outright political deadlock is making this fail. Basically, "You can lead a horse to water, but can't make it drink."
The problem is banks are soaking up productivity by issuing money ahead of wealth creation. This sees them appropriate gains. It also has a distortion effect because people doing work who are clever see that there is no point working to create wealth as the real gains are to be made in appropriating wealth. Here you get eventually stagnation as all your physics PhDs are working for investment banks trying to arbitrage fiat tokens from .... PhDs in other investment banks.
Growth can and will return when the rentiers are lanced with land value tax, as the primary vector for money creation by banks is lending against land. When this ends growth returns.
People and institutions that already have plenty of money are "hoarding cash" (and real estate) because, after other needs are taken care of, what remains is a concern about security if something unexpected happens. They don't see profitable investment opportunities worth the risk.