Disable all block features

Hi there

Can you clarify what you mean by block-related features? GeneratePress is a classic theme and does not include custom blocks.

Okay, this snippet is probably what you need:

/**
 * Remove GeneratePress block editor features.
 *
 * Add this code to your child theme's functions.php
 * or use a code snippets plugin.
 */
add_action( 'after_setup_theme', 'my_child_remove_gp_block_editor_features', 15 );

function my_child_remove_gp_block_editor_features() {
    // Remove theme support for block editor visual features
    remove_theme_support( 'align-wide' );
    remove_theme_support( 'responsive-embeds' );
    remove_theme_support( 'editor-color-palette' );

    // This should prevent the theme's block-editor.css from being loaded
    // as it's typically added via add_editor_style() after 'editor-styles' support.
    remove_theme_support( 'editor-styles' );
}

/**
 * Dequeue GeneratePress block editor specific CSS.
 *
 * This is an additional measure in case remove_theme_support('editor-styles')
 * isn't sufficient or if styles are enqueued differently for the editor.
 */
add_action( 'enqueue_block_editor_assets', 'my_child_dequeue_gp_block_editor_styles', 20 );

function my_child_dequeue_gp_block_editor_styles() {
    // Attempt to dequeue the specific block editor stylesheet.
    // The handle 'generate-block-editor-styles' is a common convention,
    // but you might need to find the exact handle if this doesn't work.
    // GeneratePress uses 'generate-block-editor-styles' for its block-editor.css.
    wp_dequeue_style( 'generate-block-editor-styles' );
    wp_deregister_style( 'generate-block-editor-styles' );
}

Glad to hear that!