Why is a Libra/Cancer relationship a bad idea?

Libra male, Cancer female

I am in a relatively new relationship and I am wondering what makes this combo doomed from the start?

both are cardinal signs. both are bossy and proud and cancer is all emotional. though libra might love the talkative nature of cancer in the beginning, slowly it will catch his nerves. Then a lot of frequency mismatch when it comes to communication.