The F-15C/D is an Air Superiority Fighter - the F-15E is a ground attack aircraft. Fhe C-model is designed to shoot down other aircraft. The ability to maneuver at high Gs and to not be seen are critical aspects for that mission.
Keeping two aircraft (The F15 and F22) in the inventory to do the same mission is expensive. You have to have logistics support for both airframes, as well as trained maintenance personnel and pilots. You would need two repair depots, two training bases, and all the assorted support that goes with each plane. It would be as expensive to do this as to go with the F22.
You can’t stop time and I like the way our life is here in the free world. I vote to keep up with the times and to maintain our freedoms with all the newF-22’s and F-35’s that it takes.