I bet Anduin is the raid leaders boyfriend and thats how he got that sword and plate armor over all the warriors in the raid.
Seemed pretty clear to me that the cinematic wanted to portray Anduins struggle to find his own leading style by putting him in his dads armor and sucking at warrioring and then switching to priest skills instead and being awesome at it.
Being a paladin would mean being good at fighting and at priesting, which is pretty much the opposite message.