I don’t see any serious typographic issues with the OpenAI slides. Moreover, their use of the Signifier typeface is a really bold move as a brand identity. There has been no other IT company using a serif since Apple abandoned its Garamond in 2001. Signifier is a badass typeface that manages to convey the feeling of something classic and futuristic at the same time, a perfect match for a company like OpenAI.
The only problem I can see are slides like the one on the left (see below) – where all the display labels are suddenly in sans serif Soehne typeface instead of Signifier. Such slides would have looked better with Signifier for the large labels.
Not so good, where is Signifier?)
Almost good. Signifier is used for the big display text, sans serif Soehne for the small text. I would have used a bit lighter weight of the Soehne or just set it in Signifier.