You are mis-characterizing MMT. Yes, inflation is one element of the limit of MMT. But more importantly, MMT advocates focusing on outcome rather than solely using some deficit/debt number as the limiting factor.
One BIG aspect of Kelton's presentation is that federal budgets are NOT like household budgets. This is a well-worn canard by deficit/debt hawks. And she rightly points out that not all debt is equal.
To use the household budget analogy though. If you have debt from going to university, it is an investment in your future in expectation of higher earnings. If your car breaks down and you don't have cash to pay for it, debt to fix it (credit card) is prudent to enable yourself to get to work and not lose your job. But if you run up debt to party or vacation in which no long term benefit is expected, then that is bad debt.
Similarly, Republicans from Reagan to GWB to Trump blew up the debt and deficit on huge military spending and tax cuts which jolted the economy briefly like a sugar-buzz from a candy bar. But the buzz wears off and a crash follows as we saw in 2008-9 and would have seen under Trump had the pandemic not forced the issue.
When I ran for Congress in 2016, I advocated that the USA needed a new CCC (civilian conservation corp)-like program, only NOT just conservation. What I was enunciating was a version of a jobs guarantee, which Kelton does much better than I. Guaranteeing jobs at a raised minimum wage does a couple of things. It stabilizes the job market and reduces unemployment. It requires business to bid more aggressively for workers in the shrunken pool of workers while raising millions out of poverty. A jobs guarantee might actually go over better with conservatives than a Universal Basic Income.
By citing cost of the jobs guarantee you are falling exactly into the classic economics trap Kelton is educating people to get out of!
One big failure of analysis that many people make when discussing the federal debt is thinking of ONLY debt. Any accountant would tell you that a liability on one person's books is an asset on someone else's books. About 30% of our debt is owed outside the USA. [1] Yes, China is a big boogie-man in this regard, but Japan is quit close. Regardless, the foreign debt holders bought our bonds because the USA is a safe place to hold their money even in low interest periods. 32% is owed to US investors for much the same reason. Federal liability is their asset. The remainder is intra-governmental. The graph sets the Federal Reserve separate from the rest of the US governent intra-government debt for a total of 37%. But the Federal Reserve is ostensibly part of the governent anyway. So this last 37% are effectively ledger column transfers in one accounting book.
The bigger issue with your critique, in my opinion, reflects a view of economic activity and federal spending in Classical & Keynesian economics. Per my article linked below [2], one can essentially view past economic approaches as "classical" (Republican, mostly with a dash of supply side) and Keynesian (mostly Democratic). But BOTH of these economic theory systems were developed during the gold-standard, hard-money days. In fact, it was Keynesian theory that was 'radical' at the time when almost everyone thought the government should always have a balanced budget.
But what has occurred since the mid-1970s and accelerated in the last twenty years, with the internet and expanded global trade, is an economy that is nothing like what the economy was prior. Essentially the economy was not much different once we got past the medieval period to the 1960s. Sure, technical advancements occurred at a rapid pace all through the industrial age but the transformation wasn't really that different until the "internet age."
[1]
https://www.marketwatch.com/story/heres-who-owns-a-record-2121-trillion-of-us-debt-2018-08-21
[2]
