How does taxation drive value? Which taxation? There are governments that don't charge income taxes, there are governments that don't charge property taxes, there are governments that don't charge sales taxes.
Tally sticks are an early example of monetized debt as a taxation medium.
Also note that the work of legal historians such as Christine Desan who are not affiliated with MMT economists concurs with this analysis.
Also note that most mainstream economists do actually agree with the tenets of MMT when individually stated but base their disagreement on a deliberate misreading/misstatement of MMT which they then proceed to criticise.
That taxation is sufficient to drive demand for a currency is not contentious, that it is necessary is unconfirmed.