I answered this briefly above, but I could flip the question by asking, if the other approaches are so great, why haven't they found product market fit and mass adoption?
And that lack of mass market adoption really annoys me because I believe in the benefits of a Zettelkasten and it would really increase creativity and productivity across many fields if there was mass market adoption.
I disagree about the mass market adoption - compared to how long Zettelkasten has been trending (less than a year), the rise in its tooling and usage is quite phenomenal.
Could you please help me understand the basis for your point of view? Precisely what evidence are you referring to? For example, the subreddit on it seems quite small... and many of the people I know could benefit from it have never heard of it before.
The first time I really heard of it was about a year ago, and there has been an explosion in tools and articles about it. No new innovation will reach mass market adoption in that time, but Zettelkasten is well on its way.