Is that just a diffused opinion (and therefore you can argue about), or a principle (something you can still argue about, but that you have to accept if you choose to participate) of this website?
If it were a "principle", then how would people concretely "have to accept" that "no question is too trivial or too newbie"?
Let's contrast it with the "principle" that downvoters do not have to explain their votes. People "have to accept" it, in these ways:
If you ask for an SE employee to reverse an unexplained downvote, your request will be denied.
If you go on meta asking for obligatory explanations on downvotes, your request will be downvoted into oblivion.
If you pester people on meta over and over again about it because you just won't accept "no" for an answer, you'll be suspended.
At the end of the day, the person who asks for mandatory explanations can still "not accept" insofar as they raise their fists indignantly every time they get an unexplained downvote. Or I guess they could try to hack SE. But we could exclude futile gesticulations and extreme cases from consideration and agree that most people have to accept that downvotes do not have to be explained if they want to continue participating on SE sites.
Now, let's go back to "no question is too trivial or too newbie". What if Alice doesn't accept this "principle"? Well, she can still downvote a question for whatever reason she holds, including that the question is too trivial.
Is there anything that can make her "have to accept" the "principle"? It seems to me the only thing that could make her "have to accept" it would be if a downvote she cast because a question was too trivial could be annulled by an SE employee or a moderator. However, this is not something that SE employees or moderators do.
All this to say that to make "no question is too trival [...]" into what you call a "principle", then other aspects of SE's customs, which are "principles" (by your usage of the term) would have to be abandoned. For instance, the "principle" that downvoters are not required to explain their votes.