Quite frankly: telling an F/O - who has just landed a jet weighing say 180 tonnes in bad weather at night, or flown it down to 200' aal and then gone around - that s/he is somehow not competant to taxi the same aircraft slowly along the ground, is preposterous.
As is: not allowing an F/O to start the engines and taxi, yet allowing them to be PF for the take-off, and expecting them to control the aircraft correctly and safely to climb away in the event of an engine failure at V1.
Yes; there have been mistakes and accidents, but many Captains have also made mistakes and caused accidents, so that is no reason to ban F/Os from taxiing. Yes, of course, as with any phase of operating an airliner, there should be minimum experience levels imposed; so for example a brand new F/O on their first ever big jet would not be allowed to taxi until they had a certain amount of experience and time on type.