Let me share some feedback with you.
Your theme structure is highly unusual and doesn't follow the WordPress template hierarchy, even though you use the same file naming conventions, which is liable to cause confusion.
In your theme all requests go through index.php, which then gets template parts with names that are normally reserved for template files in the root directory.
So the template file for displaying single pages, page.php, would ordinarily reside in the root directory, and when a URL is visited for a single page WordPress will load page.php to build the entire page. If you look at a standard theme such as twentynineteen then the content looks like this:
<?php
get_header();
?>
<section id="primary" class="content-area">
<main id="main" class="site-main">
<?php
/* Start the Loop */
while ( have_posts() ) :
the_post();
get_template_part( 'template-parts/content/content', 'page' );
// If comments are open or we have at least one comment, load up the comment template.
if ( comments_open() || get_comments_number() ) {
comments_template();
}
endwhile; // End of the loop.
?>
</main><!-- #main -->
</section><!-- #primary -->
<?php
get_footer();
Note the first thing is a call to get_header().
This includes the header.php file, also in the root directory, and this header file sets up the start of the page by including the entire head tag and then opens the body tag.
In your custom theme you do something very different, using only the index.php file (ignoring the built-in template hierarchy) which has the head tag built in. You include a header.php template, but this is simply the visual header on the page.
By breaking with the standard WordPress template hierarchy it will be very confusing for anyone working with your theme, and you risk creating compatibility issues.
In the case of Toolset's custom WordPress archives these depend upon the get_header action (triggered by the get_header call) which is pretty-much universally observed by all themes.
I'd recommend reviewing the official theme guide's advice on template files: https://developer.wordpress.org/themes/basics/template-files/
And note that, since WP 3.0, the ability to create theme's without separate (true) header.php and footer.php template files is deprecated.
