An ontology has more structure than a mind map, and you can apply reasoners to them. It was useful for me, but it undermined a layer of obfuscating abstractions some of the technologists had created as a firewall between themselves and the rest of the org, so I lost traction for being politically tone deaf.

Mind maps are easy to dismiss because they are a unifying abstraction created by someone's point of view, which must compete with every other point of view in the org. Once you model it, it implies responsibility, accountability, and that can disrupt the relationships that people have invested in.

The act of documenting something well also adds newly competent stakeholders to decisions, which has the consequence that it dilutes authority in the org.

In this way, mind maps can get a reputation for being naive technology solution to a problem that isn't actually a problem, because the nebulous relationships they expose in fact already work for someone. The helpful guy with the mind map just doesn't 'get it'.

Personally, I look forward to ontologies becoming more common in orgs, as they are immensely powerful for getting everyone aligned on a body of knowledge - assuming that's what one is aiming for.