Jesus contrasts those who 'do not see' with those who 'see.' The critical difference isn't about intelligence, but about humility and the willingness to receive truth.
The 'seeing' and 'not seeing' Jesus refers to is primarily spiritual. Those who 'do not see' are the humble, the teachable, those aware of their need for truth and perhaps feeling lost in spiritual darkness. When Christ’s light shines on them, they are able to 'see' – they gain understanding, find the way to God, and recognize Jesus for who He is. On the other hand, those who 'see' are the self-assured, the proud, those who think they already possess all the truth and wisdom (like some of the Pharisees). Because they are so convinced of their own sight, Christ’s truth doesn't enlighten them; instead, it starkly reveals their blindness, hardening their hearts and confirming them in their error. Their self-proclaimed wisdom becomes a barrier to true spiritual sight.