At its simplest, the difference between celebrity-branded feminism and a feminist movement as a social and political force is that one is about individuals and the other about systems. Individual celebrities are great at putting an appealing face on social issues. But the celebrity machine is one that runs on neither complexity nor nuance, but on cold, hard cash. How much can celebrity feminists do if their prominent voices emanate from within systems – the film, TV and music industries, for starters – in which gender inequality goes generally unquestioned? Emphasising the personal empowerment of individual actors, comedians and pop stars – whether for itself or in relation to others – only serves to pull focus from the ways in which their industries make money from stereotyping and devaluing women.

Is it celebrities’ responsibility to fix those industries single-handedly? Of course not. But it is also not ridiculous to suggest that publicly taking on feminism as a pet cause should ideally be more than just basking in the media attention you get for taking that stance. Again, paragonhood is not the goal, but at the very least, boning up on current feminist issues and perspectives will prevent more unfortunate incidents such as Patricia Arquette’s wage-gap fiasco.

In continuing the dialogues about equality and representation, small shots of honesty and transparency go a long way. Actor and comedian Amy Schumer is among the celebrity feminists who have been tagged as problematic, but she has also been refreshingly unwilling to buy into the women-are-on-top-now! media spin that’s been amplified by her own speedy ascent to Emmy-winning fame. In the autumn of 2015, as Madonna’s Rebel Heart tour took over Madison Square Garden, Schumer served as Madge’s opening act and promptly took aim at the idea that it’s a new, exciting day for women in Hollywood.

“Why would it be exciting?” she asked. “In an industry that judges you solely based on your appearance, when you know that every day you’re just decomposing, barrelling toward death while smaller, younger starlets are popping out, and you know you’re just six months away from having to wear a long white button-down and trying to fuck Michael Douglas at a Thanksgiving party? No. It’s not an exciting time for women in Hollywood. Are you serious?” The bit echoed her instantly viral 2015 sketch Last Fuckable Day, in which Schumer finds Julia Louis-Dreyfus, Tina Fey, and Patricia Arquette lunching in the woods to commemorate Louis-Dreyfus’s passage from, in casting terms, “believably fuckable” female roles to ones “where you go to the wardrobe department and all they have for you to wear are long sweaters”.

Schumer’s cutting honesty is an exception that she is able to get away with in part because her medium is comedy – but, more importantly, because, with her own successful movie and Comedy Central show, she has more control over her career than many of her Hollywood peers. Former romantic-comedy mainstay Katherine Heigl is an example of a woman whose honesty about the treatment of female characters hasn’t gone nearly as well. After her breakout role in 2007’s Knocked Up, Heigl told Vanity Fair that she found the film’s plot “a little sexist” in its portrayal of “the women as shrews, as humourless and uptight” while the men are “lovable, goofy, fun-loving guys”. She was promptly branded “difficult” – with even ostensibly feminist websites such as Jezebel frowning on her bad form – and her career foundered. Who knows whether Heigl’s relatively tactful criticism would go over better in the brave new, slightly more woman-friendly film environs of today, but at the time, her treatment in the media served as an effective warning to other women to keep their lid on their opinions.

Several years later, the spotlight was on another woman who was deemed insufficiently grateful: although she didn’t call out the film’s content, Precious star Mo’Nique was pilloried for her diffident approach to promoting the film and campaigning for the best supporting actress Oscar – which she eventually won. In an interview with the Hollywood Reporter, the actor recalled Precious director Lee Daniels telling her that she had been “blackballed” in Hollywood because of her unwillingness to “play the game” – you know, the game of cuddling up to an industry that regularly erases or sidelines women of colour.

Cautionary tales such as these might help explain why celebrity feminists (and the media that flocks to them) seem more comfortable with feminism as an identity than with its substance. Then again, there aren’t many media outlets pressing them to talk specifics. “If you’re a celebrity, you’re able to capitalise on the zeitgeisty moment that feminism is having in popular cultures,” notes J Maureen Henderson, a writer and self-described “millennial expert”. “You can say, ‘I’m a feminist’, and we’re not really going to ask you to put your money where your mouth is, to look for that in practice in the roles that you choose or the collaborators that you work with or the songs that you write. It’s enough that you’ve self-identified – that gets the headline, and living the practice is much less interesting to us, it seems.”

Furthermore, there’s no real incentive for celebrities to back up their identities with action. Sure, some corners of the feminist blogosphere might want to hold their feet to the fire, but the feminist blogosphere isn’t paying their bills or casting their next project. Shortly after her HeForShe speech at the UN, Emma Watson announced that her next film was a live-action remake of Beauty and the Beast, the most heartwarming Disney tale ever to be based around Stockholm syndrome. What a great opportunity for the newly crowned Top Feminist of 2014 to make connections between her global cause and a story about a woman who falls in love with man who overpowers her and locks her in a castle! Can’t wait to hear what she has to say!

OK, so Watson’s individual belief in feminism isn’t compromised by taking on the role of a kidnapped princess, just as, say, George Clooney’s activism on behalf of political and journalistic ethics didn’t preclude him from voicing Fantastic Mr Fox’s very unethical eponymous animal. With feminism as both a Hollywood buzzword and an identity she has taken on, it is not illogical to think Watson would want to speak to how it informs the roles she chooses. But, again, the media outlets that have made her feminism a focal point of coverage aren’t asking. It’s a pretty good illustration of the fact that while most celebrity feminism is no doubt individually well-meaning, it often has no tangible connection to the images and fantasies we pay those celebrities to construct.

In writing about the celebrity-feminist phenomenon for this newspaper, writer and cultural critic Roxane Gay, who authored 2014’s Bad Feminist, put it plainly: “So long as we continue to stare into the glittery light of the latest celebrity feminist, we avoid looking at the very real inequalities that women throughout the world continue to face. We avoid having the difficult conversations about the pay gap and the all-too-often sexist music we listen to and the movies we watch that tell women’s stories horribly (if at all) and the limited reproductive freedom women are allowed to exercise and the pervasive sexual harassment and violence too many women face. We avoid having the conversations about the hard work changing this culture will require.” It’s as though feminists are becoming part of a celebrity movement, rather than celebrities joining up with a feminist one.

As with branding, celebrity isn’t about complexity, but about offering up an enticing package that the largest number of people can understand with the smallest amount of effort. Which is why it seems important to approach and query celebrities in a way that corporate media will never do. Instead of asking celebrities how they define feminism, we should ask how they enact it in their work and their communities. Rather than focusing on the clothes they wear when agitating for causes, we can find ways to amplify their messages.

These are not unreasonable requests, but we’ve been conditioned to think they are by a mediated celebrity culture. If celebrities truly have a stake in feminism, it can no longer be about who is “bravely” embracing a maligned word. We’ve spent enough time patting actors and pop stars on the back for “redefining” feminism with their beauty and appeal, or “changing the game” simply by showing up and agreeing that, yes, totally, we should all be equal. Media and pop culture have to help change the narrative whereby simply claiming a feminist identity stands in for doing work in the service of equality. It can no longer be about who says they stand for feminism, but about how they stand for it. Like past Hollywood stances on Aids awareness, environmentalism, antiwar activism and more, celebrity feminism may well fade out to make way for the next big thing, but while it’s here, we have a small chance to refocus the spotlight.

Extracted from We Were Feminists Once (£17.99, PublicAffairs), published on 19 May. Buy a copy for £14.39 including free p&p at bookshop.theguardian.com.