We assume, from the outside looking in, that acting is a glamorous life where everything is perfect. However, according to Emma Stone, actresses have to deal with a bunch of the same crap that the rest of us do. As a woman, Stone has to deal with that much more. While the actress says she doesn't want to assume that the problem is one of sexism, it's difficult to dispute that based on the evidence.
There are times in the past, making a movie, when I've been told that I'm hindering the process by bringing up an opinion or an idea. I hesitate to make it about being a woman, but there have been times when I've improvised, they've laughed at my joke and then given it to my male costar. Given my joke away. Or it's been me saying, 'I really don't think this line is gonna work,' and being told, 'Just say it, just say it, if it doesn't work we'll cut it out' --- and they didn't cut it out, and it really didn't work!'
Some of these issues could be chalked up to particular filmmakers just not being interested in collaborating. While many directors view filmmaking as a team effort, and they want input from the actors, some just don't. They see the movie as their vision and don't want anybody messing with it, even if Emma Stone can tell you when your line is bad. However, when the actress improvs a line, they clearly like the line, because they keep it, but then they give it to the guy to say instead, that certainly smacks of sexism. The people doing it may not even be conscious of it, but that's what sexism looks like. In the interview with Rolling Stone, Emma Stone apparently went into further detail, but she did so off the record so we don't know what she said. We're going to guess it wasn't nice.
Everybody wants to feel like their contribution is appreciated, regardless of what job they're doing. Bringing up opinions should not be viewed as hindering the process, that is the process. Everybody involved is trying to make the best movie possible. Whether Emma Stone is being ignored because she's a woman or simply because the director or writer doesn't want to listen to anybody else's opinion, it still sucks for the person trying to help.
Emma Stone says that she likes being "a cog in the machine" but clearly she still wants to see that machine produce something great and be part of that. Not every idea is going to be a good one, but if you don't consider every idea, you won't find the great ones. Also, let Emma Stone tell her own jokes. She was probably funnier than the guy anyway.