I do think you can break the game that way though. I don’t think a game should have to physically make that impossible to not be a crappy game. It was the same with every edition of WFRP and Dark Heresy.
It needn't be "physically impossible". It should definitely be expensive, and require painful sacrifice elsewhere. That's just not the case in WFRP4.
I can't speak of Dark Heresy, but WFRP2 does not allow you to trivially boost your Fellowship score, for instance, to completely short-circuit the social aspects of the game. More importantly, as long as you don't base your resolution outcomes entirely on "degrees of success" (2E's term for Success Levels) it's fine to pitch 80% Charm against 30% Willpower (or whatever is suitable for the encounter at hand). It is the combination of allowing players to boost individual skill scores without having to also increase other related values AND the opposed test system that truly breaks the game.
This is not a case of a munchkin merely putting all her XP into Charm/Fellowship at the expense of never leaving her initial career. This will happen naturally to balanced players that just are never held back by the system, players that might not realize the game isn't equipped for the very natural choices the game allows them to make. (Here I'm referring to the fact that while heroes in D&D gain very high attack scores, for instance, that is never a gameplay issue since the foes you are supposed to fight gain very high Armor Class scores. But WFRP4 monsters and NPCs just never are designed with this in mind; almost as if the creatures are written with 2E in mind, completely unawares that the system has abandoned most every check and balance...)
Unlike most games I've encountered WFRP4 does break the game. It's a glaring flaw, and one that didn't need to be there. But still - had this been one out of a few areas where WFRP4 did something wonky or bad compared to other games it would be fine. Especially if it also did some or many things right or better than the alternatives.
Since my comprehensive coverage of the game has shown me that it does not do that - almost every single thing added by 4E not already present in the Warhammer lineup makes my WFRP experience worse: slower, more complex, fiddly, hard, changing the way the world works in ways I don't appreciate, and/or outright broken - I can't find
any argument to play it. It's an example of irredeemable effort.
That is, any argument other than possibly "it's there" (and its cousin "I like physical books and can't find a used copy of WFRP2 conveniently enough"). Even there I sincerely recommend you look elsewhere. Just to repeat a single suggestion: the Warlock! game from Fire Ruby designs.
As for the argument "since there exists people liking WFRP4 Zapp must be wrong" you will simply have to watch me shrug. I am not going to enter the rabbit hole of trying to understand every person. Besides I would struggle to find nice things to say of their behavior anyway.
Have a nice day