The writing of TNC is simply terrible, period
First of all, they detail in the first game that the Nazi super soldiers are literally cyborgs that are part machine, part man and their armor is grafted to their bodies. There's no way they could've gotten an intact super soldier body to transplant BJ's head onto. Besides, this new super soldier body has never been lampshaded, nor even being hinted before. And no, having it just lying around the sub before isn't just enough. There's no justification why it's headless in the first place nor any reason why Nazi made it that way (and they don't even seem to actually use such bodies for super soldier purpose. Besides, even if it really is, considering that this body lacks a head, it's safe to assume that Nazis are skilled at head transplant and it's how they make their super soldiers. However, Seth has claimed that he invented such process only recently when he put his cat's head to a monkey. The body literally exist just as a deus ex machina for BJ to survive, with no in-universe justification whatsoever. It's tell, not show
Second, the tone is all over the place. While TOB and TNO is dark and depressing, it still delivers the story better and made players immersed with the pacing. TNC on the other hand, allows itself to be more humorous and light-hearted. This is bad, because all the humor that the writers bring into the game feels very out of place. I know that they wanted the game to be close in spirit to a grindhouse movie, but in my opinion, it does not work well. And the humor itself is just not very good. There were only a handful of jokes in both TNO and TOB, but they stood out for this exact reason! Those games definitely knows when to take itself seriously, unlike TNC which will stereotypically undermine moments of gravity with comedy. The game literally interrupt a serious moment to deliver a poop joke; this is Marvel level of humor of the worst type. Devs basically injected post modernism stupidity and girl bosses, and mixed it with teenage level humor. Last game (Youngblood) is the culmination of trying to go even a step further than that. And don't get me started with a poorly disguised author's fetishes
Third, the characters are badly written. They're not really interesting and there's not a lot I can say about every new character, since they are so forgettable. And I get the feeling that the writers never really cared for them too. For example, in the beginning of the game they introduce Grace. She's a girlboss resistance leader and Spesh, her husband, is a nutjob conspiracy theorist. Well, they kill the husband halfway through the game and he never gets mentioned again, it's like he never existed ! That aside, none of the new characters are good. There's no chemistry in the group whatsoever, it's like a Michael Bay movie where every character is an asshole to others for the sake of being an asshole (seriously, it's very irritating to hear their obnoxious ramblings). It's like the writer think the amount of curses and swearing equal a strong leader. The game has too much bloat and edgy narratives