I'm not sure how that paragraph gave you the understanding that "every engineer must have an opinion". It explains that the most senior/influential/knowledgeabl

I'm not sure how that paragraph gave you the understanding that "every engineer must have an opinion". It explains that the most senior/influential/knowledgeable engineers must have an opinion because they're the ones making the decisions. In that context, the decision is the opinion; not having an opinion is the same as not deciding, which is obviously bad for the person/people responsible for deciding.