Where MOOCs may provide quality instruction for many, detractors often cite that very fact as its biggest failing.

Where 引导的从句在句首，一定是状语从句，不可能是定语从句，定语从句需要先行词。本句的先行词在哪里？

这实际是一个地点状语从句。网友应该知道这个谚语：

Where there is a will, there is a way.

有志者，事竟成。

（在有意志的地方，就有通向成功之路）