Shanghai Airlines (FM) are absolutely fine. They're not Singapore Airlines in service terms, but the planes are safe and well maintained to international standards. The fact they have made it into the Star Alliance should give you some additional reassurance.

The English language websites of many Chinese companies look "scary", though that is simply because most of their customers at the moment are Chinese. It is not a reflection of how good or bad the company is (you should see some of the shockingly bad Chinese language websites some major western firms operate, including airlines).