Mikehotel152, how do captains get to learn the taxiing - they obviously haven't taxied an aircraft with 200 people on board before? I guess during their sim sessions and line training under supervision. Why do you think the same can't be done for FOs? Sure, cadet straight out of flight school with no "big" airplane experience needs more practice and couple of more pointers, but it is still successfully done at many Airbus operators without major incidents.
And as always, both airlines and captains can impose limits on when an FO can taxi, e.g. no LVO, no narrow or slippery taxiways, etc. If you can put limits for FO as PF (wind, visibility, ceiling), so they still get to fly and gain experience, don't you think the same would apply to taxiing the aircraft?