There is more to MMT than just the Functional Finance parts, but that was the part of MMT that always generated the most heat in online debates. Should MMTers declare victory?
At the minimum, I would argue that there is a positive element to this development: it is much harder to make bald-faced lies when discussing fiscal policy than was the case in the 1990s or earlier. As such, conversations needs to gravitate towards discussing overheating, not vigilantes.
That said, there is no guarantee that this will be a golden age of economic debate. Overheating risks can be misrepresented in just the same way that bond vigilante risks always were. Furthermore, the U.S. Republican party is currently in disarray, but they will eventually get their political footing. The "oh no, the debt level is a really big number!" story has been so effective for so long that it will not be abandoned. Free market intellectual bubbles will thus gravitate to debt vigilante stories, which means that the topic will still be debated.
From my perspective, this is a concern since I need to decide whether to re-write comments in my manuscript -- we're all MMTers now, yay! My gut reaction is that any such sentiments are premature.
(Update: having just written this, saw my first comment about “unsustainable debt.” Yes, too early to think things have changed.)
(c) Brian Romanchuk 2021