The theory that the Na-Dené languages are related to Yeniseian languages appears to be generally accepted, even if not considered fully proven. That said, this

The theory that the Na-Dené languages are related to Yeniseian languages appears to be generally accepted, even if not considered fully proven. That said, this acceptance appears to be driven in large part on the basis of "okay, we do see that these languages could be related" with stronger reservations on any actual reconstruction of the relationship--the author of the theory himself seems to be accepting of this viewpoint [1]. So at the end of the day, I have to agree with the assessment that the connection of the two utterances is too strong. And it even looks like the author of the first proposal linking Na-Dené to Yeniesian would agree with this assessment! [1] See https://www.degruyter.com/document/doi/10.31826/jlr-2012-080110/html https://www.degruyter.com/document/doi/10.31826/jlr-2012-080..., which is written by the main author of this hypothesis.