I think the point is that the earlier gender-neutral advertising worked
I question that. It worked so well they spent the best part of 40 years trying to fix the problem. They've been researching initiatives to bring in female customers since the 1970's, from about the same time as those ads. If the ads were the solution why the research?
So, there's no direct evidence that it worked. People don't overhaul things that just worked by themselves. The only reason we focus on the "boys" stuff like Lego Space is because those succeeded in the marketplace, they had concurrent lines like Duplo and Fabuland which were gender-neutral but failed in the market. They promoted Fabuland for over 10 years, but it never sold, and it wasn't because they were deliberately undermining it or anything, they poured money into the marketing for that, as well as the line that succeeded.
So, it's the benefit of hindsight where we only focus on the successful Lego ranges and note that they were marketed to boys - they marketed all kinds of stuff, but only a few lines really sold. So, it's disingenious to show TV ads for the successful lines and ignore the ads for the unsuccessful lines, implying they ONLY ever made Space Lego and Lego Technix, which were marketed to boys for good reasons - that's the core demographic who like shit like that.
But, there's also the idea that the Lego ranges like Lego Space are too "boy stuff". So make it less "boy stuff", but if you make it too "girl stuff" we'll also crucify you. What's the solution: make all the blocks the same size and grey perhaps, and don't attach stories to them? Then, everyone will be happy because they appeal to nobody.
BTW there apparently is Lego Disney Princesses, so there are movie tie-ins aimed at girls as well as things like Star Wars, Indiana Jones etc. If you get pissed at that, maybe you can point me at some ideas for better pro-girl Lego movie/game tie-ins?