When is a memory palace the wrong tool?

When the goal is understanding or unordered facts — palaces excel at ordered retrieval, not comprehension or single stray facts.

Reach for something else when:

• You need to understand a concept, not recite it — that's elaboration and practice, not placement.
• The information has no useful order and is a single item — a palace is overkill.
• The material is best learned by doing (a motor skill, problem-solving).

A palace is a superb retrieval and ordering device. Use it for what it's for, and don't mistake a vividly-stored fact for a genuinely-understood one.