I question "good enough" attitude. For anything more serious than dad's pizzeria website certain minimal knowledge should be there in the head of front-end developer.

For example, if the house has been wired by an electrician, who does not know what Ohm's law or Joule's law is about is disturbing. (well, if a theoretical physicist wires the house, it may also be disturbing... but it's less likely the physicist will not at least glance some documentation).