Categories and subdirectories not filtering

I’m having a problem with categories and subdirectories not filtering properly - this can be observed on the Articles (subdirectory), Projects (subdirectory), and Development (category) pages here: https://blog.adamelnaggar.com

At the moment, all of the published content is appearing on all of those pages, no matter what category or tag has been applied.

Here is my default list.html and my config file:

list.html

<!DOCTYPE html>
<html lang="{{ .Site.LanguageCode }}" prefix="og: http://ogp.me/ns#">
{{ partial "head.html" . }}

<body>
  <article class="posts">
    <div class="row">
      <div class="col-xs-12">
        {{ partial "header.html" . }}
        <h1 class="post-title">{{ .Title }}</h1>
        <div id="posts-list">
          {{ range (where site.RegularPages "Type" "in" site.Params.mainSections).GroupByDate "2006" -}}
          <section>
            <h1 class="site-date-catalog">{{ .Key }}</h1>

            {{ range .Pages }}
            <div class="row posts-line">
              <div class="posts-date col-xs-3 col-sm-2">
                <time datetime="{{ .Date.Format "2006-01-02 15:04:05 MST" }}">{{ .Date.Format "Jan 02"}}</time>
              </div>
              <div class="posts-title col-xs-9 col-sm-10">
                <div class="row">
                  <div class="col-xs-11 col-sm-10">
                    <a href="{{ .RelPermalink }}">{{ .Title }}</a>
                  </div>
                  <div class="col-xs-1 col-sm-2 posts-categories">
                    {{ range .Params.categories }}
                    <div class="posts-category">
                      <a href="/categories/{{ lower . }}/"><strong>{{ . }}</strong></a>
                    </div>
                    {{ end }}
                  </div>
                </div>
              </div>
            </div>
            {{ end }}
          </section>
          {{ end }}
        </div>

        {{ partial "footer.html" . }}
      </div>
    </div>
  </article>

  {{ partial "scripts.html" . }}
</body>

</html>

config.toml

baseURL = 'http://blog.adamelnaggar.com/'
languageCode = 'en-us'
title = "Adam El's Blog"
theme = "yinyang"

[permalinks]
    categories =  "/:section/:slug"

[author]
name = "Adam El-Naggar"

[params]
mainSections = ["articles", "projects"]
homeSections = ["articles"]
headTitle = "Adam El's Blog"
description = "Articles about my experience growing my small business and building online side projects."

[[params.socials]]
name = "Articles"
link = "/articles/"
[[params.socials]]
name = "Podcasts"
link = "/podcasts/"
[[params.socials]]
name = "Projects"
link = "/projects/"
[[params.socials]]
name = "Subscribe"
link = "/"

[markup]
    [markup.goldmark.renderer]
      unsafe = true

Any help would be very appreciated - this is driving me up the wall!