It's true...we all have an opinion and no one is ever right all of the time or even some of the time. We get caught up in it and can't see past it. There are millions of business books that tell you exactly what that person's opinion is, and you can take it or leave it.
Consultant's get a bad wrap, sometimes it is well deserved - and sometimes it's because the person hiring them aren't ready to change their opinion - not even one little bit. Many come in and want you to change everything to match their "opinion". You don't have to re-create the wheel to improve it, but sometimes a little refresh doesn't hurt!