I was born a maker, and I've been an Entrepreneur for six years now (and a wannabe for much longer before that) and I think the worst advice I've got was from people who had never taken a step of the journey.
People with academic (or other) credentials who advise you based on theory and completely miss the point of entrepreneurship. They know about the theory of sales funnels and marketing strategies and much more but they've never made a cold call. Or a sale for that matter.
The best advice I received was from my godfather, who is an entrepreneur and salesman. That advice was simple, brutal and actionable: "If you can't sell it to a customer, how do you expect to sell it to a salesman ?". That made me realize that you don't stand a chance at success if you can't convince anyone.
A good startup advisor understands all of the field he's advising about and knows what a startup is.
He knows how to apply his knowledge to the constraints a startup faces and how to deliver that wisdom in regular words to support the startup's decision process.