In what ways could the failure to enforce conscription weaken rome

Conscription means the forced enlisting of the people of a county into national services, the term is mostly used for military enrollments. In Rome the conscription was enforced to a certain or some certain classes of people which left a little choice for them to choose the skilled people. For example people chosen for military might have come from farmer class who know nothing about operating a war machine or anything about the war or military which ultimately weakened the Rome. If there are less farmers in the country that simply mean there is less food to process also, another was a country could get weak.

Or the elite class was left out who already were not contributing to the good of society.