I did research using Topic Maps. One of those meaningless R&D projects where EU burns millions to no avail. It paid well though, and I could attend conferences around the world.

As for the usefulness of the Topic Maps, Mind Maps and ontologies in general... they are useful instantly for the person who composes them as a way to organize thoughts. Pretty much what Notion, Evernote etc are doing, but with much less elegance.

They are utterly useless as a way to share knowledge.

Also, even 20 years ago, the field was full of old farts wasting everyone's time and consuming salaries. I doubt it changed for better.

To this day, topic maps still provide me with my go-to (meta) model.

Topic maps truly provide a straightforward organizational metaphor. The foundational topic maps concept —comprising topics, occurrences, and associations— achieves a balance between simplicity and clarity while offering sufficient structure. This allows you to effectively translate your mental model of a domain into a corresponding topic map representation.