With that said, if push came to shove, the electronics on the F-22 could be quickly replaced/augmented to either have a focused IRST ala the SU-35 or a 360 system like F-35's EODAS. Your argument is in line with "It would be difficult to restart the F-22's production line." Sure, but neither doing that or updating it would cost nearly as much as the amount of money that went into the F-35.
I think IRST wasn't made a priority because the US expects to have AWACS wherever they operate and the F-22s to shoot based on AWACS data without ever actively emitting themselves anyway. That or planes toggling radar one at a time and passing data via datalink to their squadron, which makes them fairly safe (at least that was the idea with datalinks).