Gatekeeping is the activity of controlling and limiting access to a thing. In hobbies, fandoms, and communities a gatekeeper will usually take it upon themselves to limit access by deciding who does, or does not have the right to have access, or to identify as a member of a community. An example of this obnoxious, and generally douche bag behavior would be a person saying “I love the Wii, as a gamer I’ve always been a fan of Nintendo” to which the gatekeeper might respond “Wii? REAL gamers play Xbox or Playstation”. They take it upon themselves to exclude a person for not meeting THEIR predetermined expectations of what a member of that community should be. In the Warhammer community gatekeepers have begun to take up arms over Games Workshops latest attempt at expanding their reach to a younger audience through their “Warhammer Adventures” books.
The Warhammer Adventure books are aimed at a younger audience, and thus have adapted their narrative, and art style to fit their younger target. The stories remain within the realm of the Warhammer universes they represent but appear to tone down the grimdark just a bit, while not eliminating it all together. However, for a fandom where female super soldiers is more unbelievable than FTL travel achieved by flying through hell, this kind of reimagining of their fictitious universe is tantamount to being slapped across the face. Frankly it’s a little ridiculous. It is important to understand though, that the negative sentiment is not universal across the entire fandom, and that there is indeed a large portion of the community which welcomes to new series.
A lot of the hate comes from an extremely conservative portion of the fanbase which views the release of Warhammer Adventures as an attempt to dilute the adult oriented themes in the franchises they love. For the Warhammer 40k community specially, they see it as dilution of the grim darkness and forced inclusiveness within their franchise. A lot of the hate for the Warhammer 40k portion of the Adventures series comes from the fact that the characters appear to go against the norm, as one of them is against the use of any and all weapons, and the other is a child running away from military conscription. This is seen by some of the more extreme members of the community as an “SJW” take over of the franchise with some members of the community such as Instagram user @SexyYellowGuy (A painter featured by Games Workshop on several occasions) calling this a “Social Marxist” take over (give me a break).

Source: Instagram.com/SexyYellowGuy
The truth is that this is, in the long run the release of these books is beneficial for the hobby.
Let’s be real here, as emotionally invested as we all get into our hobbies, the companies that create our favorite franchises are businesses first. These businesses have to find ways to create loyal customers who will bring repeat business, but at the same time they have to find ways to create new customers. They have to find ways to secure the future of the business by creating new loyal customers. Warhammer Adventures is a great way to create customer loyalty as it targets potential future customers at an early age. It creates interest in the different Warhammer franchises at an early age, which can then be translated into interest in the games, the miniatures, the Black Library books, the video games, as the kids grow up with this franchise as a part of their life. Yes, this spinoff is less dark, and more kid friendly, but that’s because it is AIMED at a younger audience! The belief that this version of the franchise will somehow dilute the whole brand as a whole is contradicted by the fact that other franchises have undergone similar treatment, with much success. After all, how many of us were familiar with Batman animated series, an arguably cartoony take on Batman, but then grew to love the darker version of the Dark Knight in the comics and films? How many of us were introduced into Anime as a whole through silly or kiddie franchises such as Pokemon, only to dwell deeper into much more complex, and dark franchises?
People need to learn to take this for what it is, it is an attempt to create customer loyalty by getting to future customers while they are still young. It is a method by which the franchise assures its survival and continued success into the future. It is also a spin-off which does not interact or dictate the course of the main franchises as a whole. In the end if you still can’t get over your salt, the simple solution is to not buy the product and go on about your day! Let people enjoy things.