If they run just the exit node they still can’t de-anonymize you right?
If “deanonymize” strictly means perform a timing attack using info you have from the beginning and end of the circuit, then by definition you’re correct.
But if you visit an identifying set of websites and/or ignore TLS errors or … they can still deanonymize you.
Ignoring TLS errors might mean you’re ignoring the fact your exit relay is MitM attacking you.