Good people end up giving bad startup advice in two ways.
First, it happens when the advice is given irrespective of which stage of the startup lifecycle[1] the company is in.
Second, it happens when opinions are given about whether the whole idea is “good” or “bad”. Experts can often provide excellent insight about the practicality of a specific element of the business model, such as the channel. But since any number of those pieces may be swapped out along the way, it’s very difficult to judge the business as a whole. Even VCs, who do it professionally, are generally wrong.