Agree. In Venus, Jodie Whittaker merely plays herself (she even admitted this in an interview). Jessie shares much of Jodie's personality as well as her native accent. It is therefore an easy role, requiring no high-level acting.
If you haven't noticed: the Oscars are often awarded to performances of demanding nature.

She was really good, but I don't think she was great enough to earn herself an Oscar nomination. The character wasn't big enough to get some really outstanding acting out of it.