这是一个国家的情趣

I'm American, and I almost never say "so so" or "just so so". There are a lot of words like this that are part of the English curriculum for Chinese students. I think your suggestions are very good, but the problem is that if students learn English the way we (native speakers) actually use it, they wouldn't do very well on their tests, (cet 4,6, etc...) because the English on those tests is quite different from the way we speak English today.

Just so so

那是中国教材的错。不是我们的错。