I had to study it as part of business administration.

Keyensian a broader term, which is also locale based, using macro and micro datasets to guide their decision making process. It's a lot of market data and research, qualitative and quantitative. Just because one fails, it doesn't mean that they all fail, because the modelling is somewhat unique to that territory or state.

Keyensian is mainly government intervention but it's also due to that every recognised country has a government that not only manages one aspect(finances) of society, but all of it(law and order, national security, pension, nature, land and environmental protection, education, health etc.)

Central Banks should remain impartial and independent, prudent and slow in their decision making. This builds their reputation and credibility as an institution and improves their bonds (issuance of their debt) ratings and demand for that debt instrument. Think Switzerland bonds vs Zimbabwean bonds.

Merchantilsm fails, Austrian fails and keyensian fails. Keyensian is however adaptable and locale based, which is why it's all over.

Merchantilsm is Adam Smith era models where one state economy booms because it extracts another's economic power. How England gets wealth through extraction of wealth from other states. It follows imperialism or resources by conquest.

This fails because the pot is fixed, and unless you conquest or loot, you are unable to expand. There's also the problem where in order to expand the pot, you need to spend the pot, and if any failures occur, or mistakes, it can lead to a downfall of the empire.

Austrian? Look at Argentina.

But that's macro modelling level stuff.

I love economics, it's one of my favourite subjects at uni because it's not about keyensian or whatever model, but rather the study of systems.

Economies can be everything from how households or people interact with each other to government central banking and inter-state systems. There's so many economies if you think about it. I mean you've done micro