The Oscar-winning actor told The Guardian that she found it hard to understand the attitudes that some Gen Z co-stars had.
"They're like, 'Nah, I'm not feeling it today, I'm gonna come in at 10.30am'," she said.
"Or, like, in emails, I'll tell them this is all grammatically incorrect. Did you not check your spelling?
"And they're like, 'Why would I do that, isn't that kind of limiting?'"
But Foster did praise 20-year-old Bella Ramsey, saying they were an example of an actor emerging in a "vector of authenticity".
Foster knows what it's like to be a young person on a film set as a former child star herself.
She told The Guardian she felt she had to help young actors "because it was hard growing up".
"They need to learn how to relax, how to not think about it so much, how to come up with something that's theirs," she advised Gen Z.
"I can help them find that, which is so much more fun than being, with all the pressure behind it, the protagonist of the story."