Adding add_theme_support( 'post-thumbnails' );
somehow worked finally!
So my final code was:
add_action( 'after_setup_theme', 'my_child_theme_image_size', 11 );
function my_child_theme_image_size() {
add_theme_support( 'neve-blog' );
remove_image_size( 'neve-blog' );
add_image_size( 'neve-blog', 150, 150, true );
}