If there are significant cognitive issues or performance degradation with older pilots, surely you have the data to back up your claims, correct? If this was true, there would be identifiable significant failure rates or significant training issues with older pilots conducting simulator training for 121/135/91K initial, recurrent, transition and line checks.

Where are all the FSAP, ASAP & NASA reports documenting these so called claims? How many pilots have walked off airplanes or refuse to fly with these so called older pilots with these age related issues?

Are there a small minority of pilots of ALL ages who slip through the cracks, yes. However, if what you all claim was true, there would be irrefutable data to back up your so called older pilots related performance issues.