If the voltage at Ground is 0V, why is there a current flow?
The ground potential is one node in a circuit where we define the potential to be 0V. This gives us the basis to express voltage potentials for every other node in our circuit since they are always expressed relative to the ground node.
When we can choose any node in our circuit for that purpose at own will, we surely do not influence any current with that decision. And indeed: choosing the ground potential does not say anything about any current in the circuit.
With KVL we have that the voltage will essentially be depleted at the return point (ground).
KVL tells you that in a closed loop the sum of all voltages are 0. Depending on how you draw the loop, you will have a positive value for your voltage source(s) and negative values for your consumers -- or the other way around. The result would be the same: the sum of all sources and all consumers will equal 0V.
The word "depletion" should not be used here. But feel free to comment what you mean with it.
So, if this is the case then why can we have current flow (at the return point)?
As said above: the voltage potential of a node has nothing to do with the current flow at that point. In theory you could strip the cord of the power cable to your running computer and touch the wire which is connected to neutral (0V). You would not get electrocuted since there is ideally no voltage difference between you and the neutral wire. Still you know that there is a current running through that wire to power your computer.
(PLEASE DON'T TRY THIS AT HOME. ONLY A PROPER MEASUREMENT REVEALS WHICH CONNECTION IS CARRYING GROUND POTENTIAL. DON'T EXPERIMENT WITH LINE VOLTAGE!)