Having 0,0 in the back right corner is ok. It's the same as it being in the front left corner, just rotated 180 degrees. All you must keep in mind is that negative moves must move towards 0,0 and to keep that orientation in mind when setting your offsets.
Alternatively, you can change it to have 0,0 be in the front left corner, but then you must change your endstop definition to be high end of travel M574 X2 Y2 and you must change your homing files movement direction to move to the positive instead of negative. This will home to Xmax and Ymax instead of min.
The 0,0 point and the homing position don't have to match. In fact 0,0 can be anywhere, even the center of the bed.
https://duet3d.dozuki.com/Wiki/Centering_the_bed_or_setting_the_bed_origin
I really don't understand why creality did this for the Ender 5, but such as it is.
