Well you see, if you dont hire junior devs, and senior devs eventually retire... then you have no devs at all and thats usually considered bad.
So you hire junior devs... and train them to use the tools, so that they become competent with them... like literally any other job in the world.
Its like trying to argue that because your site workers on a job can use a CAT to move material way faster, now you dont need to hire new guys... which only works up until your CAT operator retires and you never bothered to train their replacement...
Any half competent manager would consider that to be a super stupid thing to have done...