But intelligence is generally appreciated in potential mates

That depends. First, it depends on the sex (some males actually prefer dumb blondes) and second, females usually like successful males -- while intelligence is clearly correlated with success, it's just a correlate and a signal, not the terminal value itself.

Also, if the floor of survive-and-breed is lowered enough (as is the case in the developed countries), the evolutionary pressures to wash out low intelligence become much weaker.

P.S.

LOL. Here is a study the abstract of which says:

We used static facial photographs of 40 men and 40 women to test the relationship between measured IQ, perceived intelligence, and facial shape. Both men and women were able to accurately evaluate the intelligence of men by viewing facial photographs. In addition to general intelligence, figural and fluid intelligence showed a significant relationship with perceived intelligence, but again, only in men. No relationship between perceived intelligence and IQ was found for women.