Could it be that you have stagnated, that your ideas are, for lack of a better word, "old fashioned"? Do you honestly think you are as good as a recent college graduate would be in this job?
It's difficult for us to see us or our work as others see it. You might want to enroll in some courses to keep your skills and ideas up to date.
The company is not going to fire you because you are too old. They are looking at the bottom line and if a younger person seems more productive, that's the direction they will take. If your work is as good or better than a younger person's they will keep you.