Reread the second paragraph. Another key element is holding firm to a position even in the face of compelling counter-arguments and refusing to work toward pragmatic solutions. How does that lead to progress from your perspective? I would argue it leads in the opposite direction.

What you summarized should be labeled as progressivism. Or simply a functioning democracy - when it’s done right in the U.S. for example, states act as laboratories trying out new ideas. When something works well in one, the others follow. It’s not a necessary condition that those ideas they try must be “extreme” as I defined it. Quite the opposite in fact.

I also find it entertaining that at least three people in the comments have taken issue with my definition of “extremism” but not one has put forth an alternative. Or even attempted to.