One level of auteur theory that I've wondered about is its political ramifications. For one, it's not a very communist theory. There's no real collectivism or equality in the idea of a singular mind behind a film. Which is probably why Godard (partially) rejected the theory later in his collaborations with Gorin. Also why Third Cinema purposefully distinguished itself from the tradition of French New Wave (a tradition of un-quality?) by categorizing it as the "Second Cinema".
Likewise, auteurship was and is a title mostly populated by white, male directors. Oh sure, there's a few notable exceptions: Agnes Varda, Claire Denis, Ousmane Sembène, etc. Nonetheless, it's important to question whether auteur theory succeeded due to the power already allocated to the canonically white, male director. And whether auteurship erases the contributions made by the editor and screenwriter, positions usually more diverse in gender and race (for instance, Marcia Lucas in Star Wars and Taxi Driver).
Personally I view auteur theory as a necessary weapon against the studio system and against the "tradition of quality", but not necessarily a theory that reflects the state of an actual film production. Truffaut, Godard, et al used it as a banner to wage war against the powers above them—producers, financiers, etc—but in doing so they also negated the work of those below them, the grips and gaffers, the cinematographers and editors. I don't believe this was their intention, but hey, they did make a theory about how filmmaking is all one dude's creation. Not exactly hard to see how that'd ignore other people's contributions.
The issue is the line between the producer and the director which is usually contentious, but I feel like most of the time it's over money issues rather than studio censorship or interference. Or if the director is taking more artistic liberties than usual regarding the script or whatever, the studio may want both the original line and the updated line shot to compare.
Certain 'auteurs' would probably get the benefit of the doubt from a producer, but only after an established body of work; unless, the director also happens to be one of the producers or an executive producer where in the latter case they would be partially financing the film- like sitting on the board and also being the CEO.
au·teur·ism. noun. The definition of auteurism is the belief that a movie should primarily reveal the director's feelings and beliefs as if he has written it himself. The theory that the director's vision should be clearly seen in a movie is an example of auterism.
the movie as a commercial product, built to spec, and designed by committee to appeal to the largest market...
So, the auteur is the "director as artist" as opposed to the "director as hired executor of the studio's will".