Many a time, I’ve come into a project where the previous “developer” downloaded a free or paid theme and used plugins to tweak the site to get the preferred output. The problem with that is how WordPress loads.
When WordPress loads, it loads all the functions in the code, loads the WordPress functionality, loads plugins, then loads themes. When you have too many active plugins, you can overload the server the site is hosted on & find out how much your hosting is really worth. For the most part, most hosts will not put many resources to WordPress hosting. Thus, you also find out how well your the theme & plugins are wrote. Unfortunately, the worst time you want to find out your WordPress themes & plugins are poorly written, is when your site so popular it’s pushing the resources of the server.
Here’s the thing. You save a lot of time, effort & frustration if you have an experienced WordPress developer to write the theme you way you want it. For example, the site mentioned earlier, among about 40 plugins, had used a plugin to generate a page of posts based on certain category. The issue I have with this, is that this kind of functionality, is built-in functionality. You don’t need a plugin to do this.
Now, don’t get me wrong. I’m not anti-plugins. In fact, there are a few plugins, I recommend. One of them is the “Force Regenerate Thumbnails“. This is a plugin that doesn’t load as part of the site output, but is a tool that is used when needed.
The point of all this is to use plugins sparingly. If you want to change how a theme outputs your content, ask an experienced WordPress developer to do it.