A sensible compromise to me is that runtime meta-programming should be used to accomplish something sufficiently generic that it can be confined to a library.

Said library can then document (and test) the interface and implementation sufficiently to add a minimal amount of complexity to the application code.

The big red flag is using this stuff in application code to hack around bad design decisions or save on a small amount of typing (there's also no barrier to its expanding and engulfing the entire codebase).