It depends on the context.
"Cutbacks are a big issue."
This example means generally people are experiencing cutbacks and it is affecting most people.
Eg: No one at your work is receiving a bonus this year and working overtime is limited.
"Cutbacks are big issues."
This is somewhat uncommon. This example could be when someone (potentially) outside of the conversation is talking about how cutbacks are affecting others.
Eg: A news reporter is talking about how different businesses across many industries are introducing cutbacks in response to a new tax law.