It's not that canon is "not to be questioned," it's just that the word means the exact opposite of personal preference. Canon is the current official portrayal of the continuity, the version presented by the current creator(s) of the core work in the franchise. It may be subject to change as the creators refine their thinking over time or as new creators take over from old ones, but what comes from the creators is canon. That's not a value judgment, merely a description. The individual can certainly have a personal preference to interpret the continuity differently, but that has no bearing on what constitutes canon, any more than a person choosing to move to Latvia has a bearing on what constitutes the United States of America. The canon is not a dogma that fans are required to obey or a perfectly consistent whole or a measure of quality or correctness or any of the other ludicrous superstitions that fans imbue the word with. It's just the stuff the creators come up with as distinct from the stuff other people come up with.