It is actually a pretty interesting point to consider deeply. Engaging with people from a position of constructive scepticism does require going in with an open mind that could realistically be changed. However, anyone who has done that once or twice quickly realises that:
1) Most people appear to have avoided thinking critically about any of their beliefs at all. At best they are repeating poorly-understood arguments from other people they respect, at worst they are playing team sports.
2) Many topical problems appear to have been settled decades or centuries ago and people are just not interested in the problems they are professing to be concerned about. This happens a lot in politics; it is wildly unusual for a new topic to come before a legislative body and most policies that make it through the process haven't been thoughtfully assessed in terms of what happened the last time people tried it. The fact that people want to tinker with the laws at all is actually a pretty big tell that the process is weird - the situation a society faces doesn't change so quickly that the laws need to be adjusted every year. It should be a rather rare thing.
It requires a sophisticated understanding of the world and an unusual grasp of empathy to maintain a level of honest scepticism in the face of those two dynamics. Trying to have a conversation about why people believe something just turns up the answer that they do and they don't have any particular reason. Most of the time there isn't anything to discuss or dig in to.