Maybe they perform not good as you expected, but at least they have the experience and lesson to know how to make it better now.
You know why USA is still most powerful country in this world, just becasue they are open to the best technology and talent worldwide.
I can not find any other reason for excluding foreign rescue experts except the chinese goverment need to control propaganda privilege and fear that malicious spreadout of miserable news and living pictures from warm-heart foreigners or few anti-communist activists.
However, saving life should always be first priority for not just lingering with government slogan.
