Well CloudFlare works if you're mainly worried about responding to HTTP(S) traffic. In this the company was responsible SMTP, POP, etc which CloudFlare doesn't really handle.
Additionally as is mentioned in the article - If the attacker knows your public IP address they can easily bypass CloudFlare by simply directing the traffic to you and not CF.
Additionally as is mentioned in the article - If the attacker knows your public IP address they can easily bypass CloudFlare by simply directing the traffic to you and not CF.