As War Is Boring's David Archibald notes, the F-22 sorely lacks infrared-search-and-track (IRST) sensors, as well as cheek-mounted, side-looking radars.
Archibald credits these shortcomings to the plane's design period, when the US Air Force placed a budget cap on developing the avionics for the Raptor.
This means that the Raptor is blind to the infrared spectrum, which has extreme value to fighter jets as all planes and missiles emit heat. The lack of side-looking radars limits how the plane can guide missiles flying at more than 90 degrees away from the plane's nose.
Meanwhile, Russia's best competition for the F-22, the Su-35 Flanker, does have IRST and cheek-mounted radars.
For the Flanker, the IRST provides a vital but limited tool against the ultra-stealthy F-22. As the Flanker has almost no hope of detecting the F-22 by conventional radar, it must rely on finding the F-22's heat signature; but, as combat aviation expert Justin Bronk previously told Business Insider, looking for fifth-generation aircraft in the open skies with IRST is like "looking through a drinking straw."
The lack of side-looking radars may prove to be a more enduring difficulty for the Raptor, however. Former F-22 Raptor pilot Lt. Col. David Berke told Business Insider that he'd avoid a close-in, turning fight if possible.
"Just because I knew I could outmaneuver an enemy, my objective wouldn't be to get in a turning fight and kill him," Berke said.
However, cheek-mounted radars have utility beyond dogfights, and by requiring the pilot to point his nose at a target to guide a missile, the plane has essentially handcuffed the pilot who could be doing other tasks.