Hi there,
you’re misreading the problem. This:
<body class="home page-template-default page page-id-2411 wp-custom-logo wp-embed-responsive post-image-aligned-center slideout-enabled slideout-mobile sticky-menu-no-transition sticky-enabled both-sticky-menu mobile-header mobile-header-sticky no-sidebar nav-float-right fluid-header separate-containers active-footer-widgets-1 nav-search-enabled header-aligned-left dropdown-hover offside-js--init customize-support" itemtype="https://schema.org/WebPage" itemscope="">
Is not an issue – what it says is there are 166 direct children within the body of the page. The Theme itself adds very little elements to the page. You can see this by testing the generatepress site.
The issue is related to the number of elements added in your content – some of the block plugins you’re using add a lot of element wrappers.