Thinking about my comment…wouldn’t it be simplier to say:
<section id="content" class="site-content blog-page">
<div class="container">
<?php if ( is_home() || ( is_front_page() && is_home() ) ) : ?>
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
<h2> There are posts but template parts aren't found </h2>
<?php get_template_part( 'template-parts/post/content', get_post_format() ); ?>
<?php get_template_part( 'template-parts/navigation/navigation', 'pagination' ); ?>
<?php endwhile; ?>
<?php else : ?>
<h2> There are no posts.</h2>
<?php endif; ?>
<?php else : ?>
<h2> THIS IS not home or front </h2>
<?php endif; ?>
</div><!-- Ends .container -->
try this, so now we know if it’s not home or if it’s no posts or if it can’t find your templates..