MMT is already at work in health care. It’s called Medicare. Just because it is currently structured as a trust fund doesn’t mean MMT ain’t at work.
MMT is already at work in energy. It was called the Tennessee Valley Authority.
MMT is already at work in biomedical sciences. It was the Human Genome Project, the Cancer Moonshot, and California Institute for Regenerative Medicine (CIRM).
There’s lots of other examples out there.
Edit: just found the CIRM impact analysis. Here’s a brief summary of the project. ~15 years ago California voters approved a ballot measure to do a tiny increase on tax and fund $3B in R&D in stem cell medicine after the Bush administration had banned a lot of it 3 years earlier. CIRM was then formed by the state government and went on to administer a cleverly-staggered series of grant sprees, where at first they were funding infrastructure-creation proposals but later shut that down and moved on to funding development-stage proposals. Over 15 years, the ~$2.7B invested without taking equity or ownership stakes in IP has returned $16B to the economy, created 88k scientific jobs, and set up the best advanced cell and gene therapy manufacturing and testing infrastructure in the world. And these are just the early impacts. They will keep growing over time because they have led to the founding and success of multiple companies, academic research groups, and infrastructural resources that enable this kind of research to succeed.