Just because an article is short, doesn't mean it's low quality
If the article answers the searcher's query, then that's a good thing.
One way search engines can judge if the result clicked answers the search query, is to track if the user returns to the search engine results page to click another result, or refine the search query. If a high percentage of users do return to the same search results after clicking to your website (comparative to your competitors), the search engine may judge that article to be low quality - but if a high percentage of users don't return to the search results, the search engine can assume the search query was answered - giving your page a high quality signal - which should mean a positive impact on rankings.
There are many other factors search engines use to judge quality. For example - is the content unique? Is the spelling and grammar good? How about the page layout - is it easy to view the relevant content?
Google have a document called "Search Quality Evaluator Guidelines" (17MB, PDF) with a lot more information: http://static.googleusercontent.com/media/www.google.com/en//insidesearch/howsearchworks/assets/searchqualityevaluatorguidelines.pdf - the most important points are summarised on various blogs if you search around.
Blogs don't have to be updated regularly to rank well
It is not better to have more articles just so it can be counted as an active blog. Old articles that are still relevant, on websites that are not updated often, can rank well in search engines.
Brian Dean's Backlinko is a good example - it doesn't have many blog posts, but some of them very rank well for extremely competitive search terms. My own website hasn't been updated for almost 12 months (yikes!), yet the Google rankings of one of my most recent posts has continued to improve - now in the top 3 for it's main keyword.
For certain search terms, you will see very old content ranking well.
Think about why articles are not getting much traffic
As long as they're still good quality - usually, I wouldn't think 5-10% of articles being "unpopular" would have any or much negative impact on the rest of your blog. Though it could depend on the size of the website.
I would look into why they're not getting much traffic. Are they even indexed in search engines?
We're getting more into technical SEO here. Every website has a crawl budget - Google, for example, will only crawl a certain number of pages per website per day (see http://searchengineland.com/google-explains-crawl-budget-means-webmasters-267597 for more info).
If you have a website with thousands of pages, 5-10% could be quite a lot of pages, and search engines could be using crawl budget on these lower value pages, when your website would benefit from having newer pages, or other older pages, crawled more often. I've seen organic traffic improve considerably on websites after pages with little traffic have been removed - though usually these pages were removed because they were low quality (e.g. duplicate content, didn't answer searcher's query well enough).
Even on small websites, it's worth reviewing old content. Perhaps you'll spot a way to improve an article, that you hadn't thought of before.
This video/transcription shows some things to consider, and some of the steps to take when reviewing low quality pages: https://moz.com/blog/low-quality-pages