Asking "what have note-taking apps accomplished?" is like asking "what have spreadsheets accomplished?" or "what have cameras accomplished?". A tool doesn't accomplish anything on its own. A tool is a means to an end.

A few days ago, someone jokingly asked if Henry Ford had a personal knowledge base in Obsidian... Well, sort of! He had something he called "jot books", where he journaled, kept notes, grocery lists, etc. Not dissimilar to how people use Obsidian. The Henry Ford Museum has fifty of these notebooks: https://www.thehenryford.org/search?Query=%22jot+book%22

How should we quantify the impact of Henry Ford's notebooks? How should we quantify the impact of spreadsheets?

Most people who accomplish anything take notes in some form, because writing is a way of thinking. We love to mythologize the tools and methods of accomplished people because we hope it will let us absorb a bit of their genius. But a good camera doesn't make a good photographer. Taking lots of photos helps.

Should you take notes? Probably. Does it matter what your method is? Probably not. Whatever works for you. Obsidian (or any other form of notetaking) is successful if it disappears and lets you accomplish your work.