Would like some advice on CSS formatting

Hi, I am looking for some opinions on a CSS formatting discussion I am having with another front end developer. I am going to try and keep it short as this has been a long discussion.

We have a developer who like to style most of his/her CSS in relation to the body.

Example:

body > .wrapper > article.main > [itemprop="articleBody"] section:first-child {  }

this is a really short example, some lines have loads of *, ~ and +

Now I find that this is so overly complicated and could be done with a simple class like

.post-content {  }

I have less experience so I am just ignored when I mention this. But I am the one that has to update the site and I am finding simple things like creating a new page and putting the blue box from page A onto the new page extremely overly complicated and I find that I a) have to make a even bigger more specific string of selectors b) I have to go through his code and change his long string to a simple class. But then as I do this everything that is after the blue box on page A has now lost some of its formatting so I have to fix that too.

I would really like a second opinion on this so any comments would be much appreciated