MMT is just a convoluted way of getting to the same answer these days…..the amount you are able to spend is ultimately controlled by printing, inflation and taxation
You could argue that partial MMT is kinda already utilised when it comes to the QE used worldworld since 2008 and then governments inflating away some long term debt

. This has gone badly in terms of overall debasement and inequality in most countries including ours
The only difference I can see with conventional theory is the belief that you can control inflation purely by taxation rather than interest rates. I personally think the tax system if far too cumbersome to change quickly, coming up with and implementing tax changes takes ages, let alone collection of those taxes.
Too many using MMT as ‘the answer’ are still intentionally/disingenuously not addressing the risks/costs/consequences of it though and Polanski is the new poster boy for this. Whether it would work long term, who knows, I’m not a prophet but there is no way this could ever be implemented into the current world without major economic shocks, probably devaluing of pound and rampant inflation, that would make truss mini budget look like a minor tremor