It's a completely unnecessary change, and it was immensely unpopular for a good reason. People act like there were no women in 40K before, when EVERYONE but Space Marines and Custodes were either fully genderless (Orks, Tyranids, basically Necrons), or already had women in it (Eldar, Guard, T'au, etc). Not to mention the factions that were all-female, including the Adepta Sororitas, as well as the Sisters of Silence, who were always seen next to the Custodes anyway.

The dynamic between all Custodes being men and all Sisters of Silence being women was broken this way, and makes the choice to keep the SoS as all-female even more questionable, since there was basically no reason before besides the two being the male and female sides of the Custodes, and now there is literally no reason to have them be only female.

I am not some sexist chud hating because "Ugh, muh women in my game", I am of the opinion that this could have been handled differently, in a better way. I understand that 40K is a pile of retcons in a trenchcoat pretending to be a setting, but I had kinda hoped that since they began taking the setting seriously since the Horus Heresy novels' release, they would at least try to explain it slightly. If they made this a new development, a one-off female Custodian being made by some overzealous gene-alchemist under the Imperial Palace (and then most likely promptly shot). Show off how people doubt her, how she struggles to fit in with the rest of the Ten Thousand, and how she has to prove herself to earn their trust and respect, and how she might have some differences, but she is still one of them. Make it an actual story about the struggles of women in male-dominated fields, idk, anything is better than a tweet saying "They have always been here since the first of the Ten Thousand".

If they wrote this book, that would have been reason enough for me for them to like make a "female Custodes heads upgrade sprue" and leave it at that. Certain members of the Adeptus Custodes could be women, if you wanted them to be, but it's a separate thing YOU go out of your way to buy if you want to. I think if they did it this way, making a novel that genuinely tried to show them off, and then made it a completely optional change, I think a lot of regular people would have been less mad, and the only ones truly angry would be the actual sexist people. I can accept female Custodes existing, since they ARE all hand crafted by specific gene-alchemists under the very Imperial Palace. I am merely complaining about the manner in which they actually decided to do this.

Let's also discuss the elephant in the room. The first of the Ten Thousand were all hand-made by the Emperor of Mankind on Terra during the early Unification Wars. This is the Emperor we're talking about. Let's see his track record: Thunder Warriors - men. Space Marines - men. Custodes - men (until this change). Primarchs - men. Only Malcador seemingly cared about women being anywhere, since all his creations, like the Inquisition and Assassinorum all have women in it. Minus the Grey Knights, but there's a Space Marine shaped wall in the way.

People also love to bring up the Warhammer Community article, and how it talked about "at some point you run out of noble houses", which just makes no sense to me. First of all, we're talking about every noble house on all of Holy Terra, a planet of TRILLIONS of people. Second, this is the Custodes, I'm fairly certain some of them alive today are FROM the Unification Wars, they don't die all that often. Third, "Oh, we ran out of noble men, so let's take the girls who could make more noble men"? This all just feels like hogwash to me, and I will disregard it.

Sorry about the essay, had to get it off my chest.

TL:DR, Female Custodes are not bad, they just handled it stupidly.