The example that comes readiest to mind is NOT, as you might think, his inability to quite understand that yes, Elly actually did feel trapped and useless and lost throughout most of the Early, Middle and Later Years. The example that comes to my mind appears about five to ten years from now when he proves himself incapable of understanding why his teenaged kids are always so moody and surly. He provides them with a nice home and nice things and it seems to him that their problems are easily solved so the hostility and depression are something he never quite understands. What he tends to not quite remember is that back when he was that age, a zit or a bad hair day or Patsy O'Connor dating another person actually felt like the end of the world.
This tendency is not one Elly shares by any means. This is because when she's not trying to jam up relationships that are being taken too seriously, she's trying to gain vicarious vengeance on girls with the body and the language. John, on the other hand, simply wants an end to the huffiness and drama without really caring too much about whatever hormone causes it. Once the kids have seen the real world and talked to someone sensible like their cousin Laura, they'll realize that it's silly to mope about who's pals with whom and be the quiet, grateful kids he 'deserves.'