Just now I discovered the "Pointer Location" dev app on Android, which tells how much pressure is being applied on the point on the touchscreen. They even have it since Android 1.0.
I know there may not be dedicated pressure sensors and it is just an estimate depending on point size.
I am saying that why didn't or couldn't Android implement "Force Touch" in Android phones? They have the pressure readings ready. They even have the method which when called gives the pressure.
P.S. I am running LineageOS unofficial build for my OnePlus One.