I fall somewhere between Austrian economics and MMT/Keynesian economics. I don't think either side, while sticking 100% true to their ideals, gets the entire economic picture correct. The economy is so unbelievable complicated and unpredictable, I don't believe anyone fully understands the full ramifications of any policy or outcome.
There video is indeed a good primer on MMT, but as others said, it only looks at it from MMT's viewpoint and ignores a few other critical parts. I do agree that austerity isn't and shouldn't always be the goal and maintaining a "balanced budget" isn't exactly prudent at all times. However, one thing that the video ignores is the idea of money itself and how that can impact ordinary people's lives when the government operates under MMT.
For example, the cantillon effect is the premise that money is not always fair and neutral. If the government is to operate under MMT policy, then that means that "money printing" (in all its forms) is being used as a means to control debt. However, that money and how it enters the economy is not fair or neutral and it is nearly impossible to "print money" and release it into the economy in a way that is fair and equitable. There will always inherently be those who receive the money first in its circulation and those who "receive" that money through its circulation later in that money's life cycle. Therefore, those that receive that money first will inherently benefit the most from that money prior to that money exerting its inflationary forces on the economy. It is those people that will receive the greatest benefit of that money. This is a big reason why there is such a wealth gap in our world under MMT because those who are closest to the money printing (ie, usually not the poor) are the ones that benefit the most.
As others have said as well, there is a limit to which MMT theory works in reality. Just because we can operate under continued deficits doesn't mean we can always operate under any kind of deficits. There are absolutely times that call for controlling the budget is prudent. At the moment our debt-to-GDP ratio is ~130 and that is far from being healthy even for MMT.
Then there is also the concepts around currency and the relationships and trade balances that take place between the countries of our world. The currencies of national governments don't exist in a vacuum and there are certain benefits that the US has as its place in the world as an economic powerhouse and the fact that its currency is a reserve currency for many nations around the world. This allows the US certain advantages when executing MMT for its budget and its citizens that wouldn't necessarily be available to other countries that don't have that same stature on the greater global economic stage.
In all, the video is a good primer on MMT, but at the same time my advice is to not become a subscriber to any single economic theory, but to try and understand the ideas of all of them as I think there are good ideas from each of them that are relevant at any given time.
