Outputs minified WP Core Block styles css in footer, only the blocks you actually use in the_content()

css.php

<?php
/**
 * Outputs minified WP Core Block styles css in footer, only the blocks you actually use in the_content()
 * Needs wp_deregister_script( 'wp-block-library' );
 * 
 * @author Ramon Fincken, ManagedWPHosting.nl
 * 
 * @param string $block_content
 * @param array  $parsed_block
 * @return string
 */
function mp_render_block_styles ( string $block_content, array $parsed_block ) {
    global $mp_block_css;
    
    if( !substr_count( $parsed_block['blockName'], 'core/' ) ) {
        return $block_content;
    }
    
    // Set
    if( !is_array( $mp_block_css ) ) {
        $mp_block_css = [];
    }
    
    $t = str_replace( 'core/', '', $parsed_block['blockName'] );

    // Set up CSS data array
    if( isset( $mp_block_css[$t] ) ) {
        return $block_content;
    }
    
    // Add to global array for usage in footer
    $file = ABSPATH . WPINC . '/blocks/'.$t.'/style.min.css';
    if( !file_exists( $file ) ) {
        return $block_content;
    }
    $mp_block_css[$t] = file_get_contents( $file );
    
    // Output all CSS just the once
    if( count( $mp_block_css ) == 1 ) {
        add_action( 'wp_footer', function( ) { global $mp_block_css; echo '<style>'; foreach( $mp_block_css as $css) { echo $css. ' ';  } echo '</style>'; } );
    }
    
    return $block_content;
}
add_filter( 'render_block', 'mp_render_block_styles', 0, 2 );

Note: style.min.css is used, not style-rtl.min.css which is also available