How to create a classified section in place of comments_template

It will be a three step process.

1. You can use comment_form_logged_in_after (for logged in users) and/or comment_form_after_fields (for non-logged in users) actions to add your custom fields.

2. Save the values as comment meta using update_comment_meta function hooked into comment_post action.

3. Get the values using get_comment_meta.

EDIT: 25-05-2022

Try this..

/*
 * This will add the fields to the comment form
*/
function wpse406058_custom_comment_fields() {

    echo '<p class="comment-form-wantto">';
    echo '<label for="wantto">I Want To</label>';
    echo '<select id="wantto" name="wantto" class="myclass">';
        echo '<option value="WANT TO BUY">WANT TO BUY</option>';
        echo '<option value="WANT TO SELL">WANT TO SELL</option>';
        echo '<option value="INFO">INFO</option>';
    echo '</select>';

}
add_action( 'comment_form_logged_in_after', 'wpse406058_custom_comment_fields' );
add_action( 'comment_form_after_fields', 'wpse406058_custom_comment_fields' );

/*
 * This will field value as comment meta
*/
function wpse406058_save_custom_field($comment_id) {

    if ( isset($_POST['wantto']) && !empty($_POST['wantto']) ) {
        $wantto = sanitize_text_field($_POST['wantto']);
        update_comment_meta( $comment_id, 'wantto', $wantto );
    }
    
}
add_action( 'comment_post', 'wpse406058_save_custom_field' );

Now you can get the value using get_comment_meta( $comment_id, 'wantto', true );

One option to display the value would be filtering the comment text.

function wpse406058_display_comment_meta( $comment_text ) {
    
    $wantto = get_comment_meta( get_comment_ID(), 'wantto', true );
    
    if ( isset($wantto) && !empty($wantto) ) {
    
        $wanttotext="<p class="wantosec">" . esc_html($wantto) . '</p>';
        
        $comment_text = $wanttotext . $comment_text;
    }
    
    return $comment_text;

}
add_filter( 'comment_text', 'wpse406058_display_comment_meta' );