It’s not a directory. Hand-crafted descriptions instead of random citations and/or marketing from the site itself is what makes it a directory. This one is a search engine. Maybe it’s a good one for its purpose, but who knows, without an ability to navigate you can’t tell.

Problem is people usually want one general search engine, not a collection of niche ones.

In my opinion, the reason they want a general search engine is that they think in their box (search -> general search). What they really want is a way to discover things and quick summaries about them: “$section: $what $what_it_does $see_also”. Search engines abuse this necessity and suggest deceitfully summarized ads instead.