Not using something to its full potential.

Inefficiency in maximizing resources or capabilities.

Underuse of available capacity or opportunities.

Failure to fully utilize a resource, skill, or asset

Not fully utilizing or making the most of resources.

Failing to use something effectively or efficiently.

Inadequate utilization of available capacity, space, or potential.

Underutilizing skills, talents, or abilities in a given situation.

Using less than the full capability of an object/resource/person.