It's often used when the effect being made is positive or beneficial. The charity event started making inroads into supporting the local homeless community.
Pro Tip 2/3
Gradual Effect
The phrase suggests a gradual process, not an immediate impact. They are slowly making inroads into the problem of plastic waste in oceans.
Pro Tip 3/3
Ongoing Action
Use it for actions in progress, rather than completed tasks. Her research is making inroads into finding a cure for the disease.