Why is there no technology available that can provide the pilots with accurate and simple information on the deceleration rate of the aircraft on touch down?
There is, and it's fitted in the A320 series.
Autobrake medium aims to provide 3 m/s/s deceleration. When it achieves at least 80% of this a little green "Decel" light comes on.
On landing, the PNF calls "Decel" when it comes on, or "No decel" if it doesn't.