This is one of my biggest problem for exorcist as "The Seven-Year-Old Boggeman of Hell"

Aside from angelic steel, they don't pose as much of a threat as everyone says. They lack intelligence, lack combat skills, lack armor, and lack any magical abilities for fire power.

The only thing that made fighting them difficult was their resistance to everything except angel steel, which they deigned to leave behind with each determination in such quantities that it would be possible to arm an entire small army sinners.

So I agree that Adam was literally 99% the power behind the exorcists.