Does that mean that anti-radar counter measures should be a higher priority than anti-IR measures?
The effectiveness of chaff has been declining as progress in electronics has increased. Essentially the newer radar transmitters and receivers are better able to handle the chaff and the missile guidance systems have sufficient processing power to separate the chaff from the aircraft. The radar cross-sections of commercial aircraft, carbon fiber usage not withstanding, is huge for missile systems designed to cope with far smaller, high performance military aircraft with radar warning receivers, automatic threat identification and classification systems, flares, chaff, electronic countermeasures, electronic counter-countermeasures, towed decoys, etc.
More complex anti-radar measures would put the airline industry and commercial aircraft suppliers in an arms race against the combined power of the world's weapons designers. I submit that is an impossible task for technical, political, and economic reasons.
Modern airforces avoid known radar guided missile engagement zones or actively target the systems. Since no airline I know of is in the business of killing SAM sites, steering well clear is the only real option, imperfect is that will always be.