I'm yet to meet anyone that actually understands MMT and doesn't endorse it. You might be the first, but I doubt it. Which bit of MMT do you have trouble with?
"implemented"? What does that mean? MMT accurately describes the monetary operations and fiscal constraints of a sovereign government (i.e. with their own currency) and from which you can predict outcomes with a high degree of reliability.
Insomuch as "implemented" means using the policy prescriptions (specifically, the job guarantee), there are no countries doing that, but various real world experiments have touched on it.
Japan had done things differently (albeit from a different perspective of mainstream economics) and is a good test case for the MMT model, especially given how many bet against the yen (and lose), implying the mainstream models are struggling there.
I said the political will does not exist (in several different ways) now you say:
> Insomuch as "implemented" means using the policy prescriptions (specifically, the job guarantee), there are no countries doing that, but various real world experiments have touched on it.
Something that you can't implement, doesn't work. In practice MMT is a smokescreen for politicians to print money for their friends.
The point is, you don't "implement" MMT. It's a useful framework for analysis regardless of what policies you choose. If we could get to the point of discussing monetary and fiscal operations from a sound basis, then we can start debating policies, but we're so far from that at the moment.