Mozilla currently recommends using 3DES ciphers instead of RC4 for backwards compatibility with very old systems like Android 2 or Internet Explorer on Windows XP.
The current recommendation comes after similar recommendations from researchers that discovered the most recent flaws in it, Cisco, Microsoft and their proposition to IETF as well as Qualys and Bruce Schneier.
The message is clear: don’t use RC4.
If you had for some reason follow the Mozilla guide, you don’t have to use this insecure, nearly 30 year old cipher any more. While you’re changing the cipher suite defaults, consider also updating to Perfect Forward Secrecy capable configuration.