"Historically modern monetary theory placed too little emphasis on the role of tax in the economy. It's my belief, explained here and here that tax and modern monetary theory are intimately linked issues. That's not because tax pays for government spending: it does not. But tax is fundamental to fiscal policy in a modern monetary theory environment. And without the funding constraint that has limited tax design to date, MMT liberates tax to be an instrument for social change as well.
https://www.taxresearch.org.uk