You must have read the fable where a man, his son, and their donkey accept numerous conflicting advice, culminating in a highly undesirable end.
Leadership, influence, and just plain etiquette requires you to listen to your co-worker. However, listening to what they say, and accepting their point of view is not the same as agreeing and implementing their advice.
Decision making is a complex effort, and you must retain the right to making your own decisions. You may hire consultants who have an “independent third-party” viewpoint. If such viewpoint is truly neutral (as opposed to just trying to sell you more products and services), you will do well to consider it seriously.
If you need to give advice, first understand your co-workers needs and earn their trust by delivering on projects that matter to them. You may have correctly identified the root cause of their biggest pain point, but they may have identified a lesser pain point as being more urgent. You have to be constantly aware of whether you are working on the root cause, or delivering a project to build credibility. Don’t confuse one for the other.
Inexperienced consultants will come under pressure and go for short term wins without understanding the big picture. Such consultants will take short cuts, create designs that don’t scale, and create a bigger mess than what they started with. Competent consultants will refuse to do business with you until they can assess the risks of engaging with you.