I love Lego. I had a big bucket of it when I was a kid, and I spent many happy hours constructing anything and everything from it.

Best of all was the technic Lego, the gears and axles and motors that formed the guts of fantastical machines, frequently purposeless but endlessly fascinating. It was also implicitly educational. When I was 14, I was the only one in my class who knew what a worm gear and a cam were.

Lego epitomises freedom and creativity. With a big enough collection, you can make anything in the world, and there's a decent chance that you'll be the first person ever to have put together those obliging little plastic bricks quite like that.

When I was a kid, Lego had nothing to do with gender and everyone played with the same bricks. Times have changed. In 2012, the manufacturer came up with what it called "Lego friends", aimed specifically at girls. The sets play up to almost every female stereotype, with lots of pink, handbags aplenty and oodles of lipstick for its denizens. What made it even more depressing was that the company claimed it was the result of extensive research into what would tempt young girls to play with Lego. Their answer was fundamentally defeatist, because it was "turn Lego into something else".

But all hope was not lost. This week, Lego announced the latest winner of its "Lego ideas" competition: a set of female scientists. The idea was dreamed up by Dr Ellen Kooijman and the new line will go into production this summer. There's a palaeontologist, an astronomer and a chemist, with a very cool dinosaur skeleton and other props. That's progress, surely? Even if, in 2014, we should be miles beyond that sort of progress.

Lego Grandma. Photograph: Jim Powell/Guardian

I'm not so sure. I want to be enthusiastic about this. I applaud all steps, however tiny, to correct the powerful cultural stereotypes that stop so many women from joining civilisation's great march towards scientific and technological progress. In 2012, men were awarded 85% of all engineering and technology degrees. In 2011, 49% of maintained co-ed schools had no female pupils who did physics A-level. Yet it has been demonstrated that girls do just as well, if not better, than boys when they do study these subjects.

Our society and our economy desperately need more qualified graduates in technical disciplines. This is a problem for everyone, not just the women who are put off a potentially fulfilling career.

Is this Lego's problem? They just make small plastic bricks, after all. They've got some female scientists in the mix now, and hooray for them. Is it their job to be nudging young children into politically correct careers?

While writing this, I had a look at the other new figures that make up series 11 of the Lego minifigures range. There are 16 in total. Male figures include a Constable, a Barbarian, a Mountain Climber (very heroic he is too) and an Island Warrior. Female figures … hmm.

Lego Cheerleader (series 1). Gimmie an L! Gimmie an E! Gimmie a G! Gimmie an O! Yaaay! Photograph: Graeme Robertson/Guardian

Lego, you are about to lose a lot of brownie points. Apart from our scientists, there is a "Lady Robot" (who exists mainly to party), a "Pretzel Girl", a "Diner Waitress" (who will boss you about if you don't agree with her recommendation of which burger is best for you), and "Grandma". I am not making those up. Read them again. I cannot tell you how much I wish I was making them up.

Denmark, where Lego is based, is famed for being better at gender equality than most other countries. Yet this year, it has produced a toy range that has traditional alpha male heroes and traditional helpless (and bossy) females. That is undoubtedly damaging to both young boys and young girls, and also to the future of society.

All right, Lego, maybe it's not your job to dictate culture and produce female mountain climbers. But then don't dictate culture by making female pretzel girls. Lego is modular. It is perfectly designed for avoiding this issue, because you can just make all the bits (hair, spears, burgers etc) and let children put them together for themselves. Why impose the stereotypes on them at all?

If only Lego had left out pretzel and diner girls, and added a female mountain climber and a female constable. Positive female stereotypes are necessary, but let's also work on getting rid of some of the negative ones.

There are lots of other gender-specific toys out there, and I think that the reason this one makes me so frustrated is that Lego is the perfect gender-neutral toy. It's amazing. People have used it to make a working version of the Antikythera mechanism, a 3D embodiment of Esher's "Relativity", a working harpsichord, a working V8 engine, and lots of modern art.

Everyone should have access to that creative world. And they can create whatever they want. If girls want to make beauty salons, they'll make them out of normal Lego bricks. If they want to make a steam engine, they'll make that instead. And if the boys want to make a bakery instead of a factory, they'll be able to do that too. No one benefits from imprisoning young minds.

Lego, I love you to bits. Those same bits have been houses and ducks and conveyer belts and musical instruments. Let's not ruin a beautiful relationship. When series 12 of the minifigures comes out, please let the children have a say about what heroes and waitresses look like. I'm not saying you should put a female physicist like me in there. But include the ingredients to make one in the future.