Not the usual type of Quora question that I answer on any of my website/blogs but it’s something that I feel passionately about so I hope you’ll pardon my one-time soap-box speech. Anyway, here goes —
There is no definitive way to know if an article has depth unless you are an expert on the subject of the article. Because depth means going into specifics that no one would know unless they were an expert.
You can check as to whether the article is full of specifics. Whether it gives comparisons. Whether it lists pros and cons. Whether it quotes experts. And so on. Whether it contains the things that would seem to indicate actual knowledge of the subject.
What you can’t do — unless you do a whole lot of research — is know if those things are credible or whether the author is simply blowing smoke in your face to make you think he/she knows what the article is about.
So credibility is all up to the reader.
As a caveat, it’s a sad commentary on communication today that so many people are willing to accept any statement that they agree with as fact without checking the veracity of the statement. I suspect that a lot of the divisiveness we see today in the media and elsewhere could be avoided if people would spend the time to actually do a bit of fact-checking.