In day-to-day life, the quality of your thinking depends so much on character. The company you keep is also important.
It’s not that intelligence doesn’t play a role. It’s just insufficient by itself. People who are mentally quick don’t necessarily think with depth, either generally or in response to certain topics. There’s no guarantee they’ll ever investigate their own opinions or question their own assumptions with any seriousness.
They can use their mental agility to dodge or immediately deflect any ideas or substantive pieces of evidence that don’t fit with their view of “how things are.” (Sometimes, these kinds of deflections help people get through the day without getting bogged down; it’s impossible to spend every moment re-evaluating what you think. But there are situations where deflections and dodges are harmful, shutting down an important line of inquiry or preventing a discussion about a proposed law. The quality and timing of these deflections, and the reasons behind them, are affected by your character – what you value, for instance, and your integrity.)
They may be clever at crafting rationalizations or arguments that seem well-structured. They may feel no need to examine whether they’re behaving with integrity; it’s enough that other “right-minded” people are expressing the same thoughts. They may prioritize “owning” someone in an argument over learning anything. Or they use their intelligence mostly for snark and viciousness.
An intelligent mind can still be a lazy mind. It can still be a narrow mind or a mind given to exceptional dishonesty. (Context matters too. An individual can display in-depth thinking in one area of life while remaining superficial or dishonest in other areas – and either not recognizing the superficiality or not being troubled by it, because it doesn’t cost them social approval.)