It can be said using HTML section or article tags does not effect search engine ranking. In a nuanced way that is true. But I'll be making the case that HTML section and article tags do or can effect search engine rankings.
Before making the case for semantic tags and SEO. ARIA devices use semantic tags, specifically with article tags they are navigation points. ARIA devices allow listeners to specifically pull up the sections of a page that have the role of article.
The article tag as the name may suggest, conveys the content within the tag is able to stand alone as an article or product description. All the information in the article tag can make sense without needing to look at other information on the page, although the article may have a link to a longer or complete article as in the front page of news sites, etc.
A web page may contain many article tags which may contain any other type of element.
SEO considerations with semantic article
The section tag conveys a meaningful relationship between elements of a section but does not have a default role, does not convey that it can be read and understood without the context of other parts of the page. A section tag can be assigned a number of roles within ARIA or merely left as is to convey that its elements are related.
Both the article and section tags convey a meaningful relationship between the elements inside them.
Some additional content in the section can help to understand the section tag.
Here we are using the role of application for the processing of an image. All of the elements in the section are related to the application.
SEO considerations with semantic section
The div tag is a default block tag. It can contain anything and does not convey any meaning. For example if a portion of page needs a wrapper element for CSS styling a div can be used.
SEO and div vs article & section
Search engines use nearby content to put togeather what a page or particular piece of content is about. And, when a link is part of that what the content on that link should be in order for the link to be relevant to this page and this page to have a relevant link to the other page. They are very good at doing so, and the div example shown should be easy for them, but not all mark up is that easy. Take the following example:
Should that be? All content is related there are two chapters or an x vs y sections.
Or should it be? there are two independ groups of content or two products, the iphone with its features and a android with it features and the iphone can not use the google play store.
There are far more complicated mark ups which could be used. Helping a search engine index content is being search engine friendly which is SEO.