It is really true, but yes there are some specific exceptions. In general: “Copyright protection does not extend to names, titles, short phrases, ideas, methods, facts, or systems.” https://www.copyright.gov/engage/writers/

You’re right that in certain limited circumstances, copyright will protect fictional characters. To protect a character, the character must be “well delineated”, and this has proven to be a pretty high bar. https://en.wikipedia.org/wiki/Copyright_protection_for_ficti...