Adults can drink Enfamil or any other baby formula.
However while you can drink Enfamil or other baby formula as an adult you would not want to drink it because it tastes nasty.
I once took a sip of my babies formula from the bottle and it was nasty and I spit the stuff out within a second and could not see how my babies could drink that stuff.
Babies however have different tastes and their taste buds are not fully developed to taste everything so the formula doesn't really taste bad to them.
However some babies will spit up the formula which means they don't like it and their stomach is not agreeing with it.
Newborns can taste and smell and will favor sweet tastes over bitter ones.
For example, a newborn will choose to suck on a bottle of sweetened water, but will turn away or cry if given something bitter or sour to taste.
Likewise, newborns will turn toward smells they favor and turn away from bad odors.
If you do try tasting some baby formula then you likely won't enjoy it either and won't want to drink it.
Also adults cannot survive alone on baby formula like babies can.