That's a lot of popular websites, sure, but how many of these websites are commonly used in China? How many of these websites even have a Chinese version? After all, not everybody speaks English.
LinkedIn has entered the Chinese market, but it's not as well-known as local sites such as 51job, Pokemon games still aren't available in Chinese, and wordpress.org is only of interest to people who self-host blogs (wordpress.com has been blocked for a couple of years). The rest, few have even heard of.
China has its own web ecosystem, so blocking these websites has only minimal impact to the typical user. It would be developers and expats who will bear the most impact.