What you're describing would not be a revolutionary discovery, it would be evolutionary. Hubble discovering the universe's expansion was accelerating is something basically nobody expected, because it's completely ridiculous. I mean think about the absurdity of that for a second, instead of just taking it for granted.

But of course it's true. The announcement was largely met with skepticism. But after it held up, it led directly to the contemporary hypothesis of dark energy and created a general frantic hand-waving not about the earliest moments of the universe, for which we will never have any certainty whatsoever, but about what's happening at this very moment!

For JWST to match this it'd need to do something like make some completely unexpected discovery effectively resolving dark energy/matter, which would sort of be the equal but opposite of what Hubble achieved. Of course the odds of it doing anything like this are near 0. On the other hand the odds of the universe's expansion accelerating were also near 0.

That, if it was not clear, is why I simultaneously support development of such telescopes and similar technology, but also am extremely skeptical that they'll provide anything of major value. Because in 99.9% of cases, they won't. But that 0.1% is worth looking for nonetheless, because you never know how large a leap it may enable.