Neo-chartalism, is wrong for exactly the same causes its previous version is guilty off, a bad interpretation of the origin of money(money wasnt created byt the state it is born historically out of social relations of cultural importance, which make an objectr have more psychological importance than others, take for example salt, or certain types of flowers in old societies all these used as a medium of exchange).
Second, it sees money much as a simbol of debt issueing towards the state, however, if you take this argument towards its final conclusion, you realize that every exchange is indeed a debt which helps in absolutely nothing when constructing or describing fiscal policy.
Form, this, it is concluded, that the state can just use as much money as it is desired, in order for different sectors to pay their debts.Meaning, that, the what the state should do is liberate money printing capacity, and let it be whatever we want it to be, in other words, we can pump as much money into the economy as we deem possible.
This argument has some heavy contradictions.Take a really simple example, if you buy some fresh bananas at 5$ taken taht your budget constraint is equal to what you spent, now, it is a given, that banana output production is limited by natural conditions, you can only get as much bananas as the soil lets you, also taking into accounts draughts etc, all this meaning that supply can´t be modified.You could say there is an "equilibrium", but if suddelny someone would add purchasing power say nother 5$, then he would have double his budget, assuming that he want to put all of that into the market, then, assuming the same supply, what would happen?, it is evident, that he could still buy all of the bananas, but he would end up with more money than goods exists, meaning, excdeeding value of titles which can claim goods, than the value of goods themselves, more demand than supply, making that money as such useless, now imagine an economy whre this would happen, with many buyers and sellers, this would ultimately leave at a clear view the fact that actual value is no there, hence if the capitalist is driven by production and wants to spend, and also taking away this excess money would be very complicated, then you have to corrrect pp, then how do tou do it?, easy, inflation.Making MMT just a "theory of inflaition financing".
There is also the problem that given the laws of capitalist production, the bourgeois, have a maximizing profit rate attitude, making investment completely tied to it, having as an ulterior conclusion, the fact that you can´t pump as much money into the economy as you want, since money will be invested into capital as much as it turns a significant profit rate for the capitalist.