The article should be original. The plagiarism percentage match should be < 5%.
It should NOT be promotional or spammy in nature.
For example, intelligently include a bunch of backlinks to some products without offering substantial value in an article.
It ought to benefit readers and impart knowledge.
Additional determining factors
If the article is generic (and therefore appeals to the general audience), it's a good candidate.
We generally avoid featuring really short articles unless they are exceptional. Nevertheless, Read Time is not the only factor.
Reactions and comments have no bearing on our choice. However, we do have a look while going through the articles.
We are OK featuring republished articles as long as they offer value. We try to highlight items that are inclusive and diverse.
We give a wide variety of authors a chance. We don't select the same authors all that often.
This is what a Featured Article looks like on Hashnode Feed Page.
A featured badge will also be visible on the article, as shown below: