Google requires apps (and updates to existing apps) to target an Android API level released within roughly the last two years — apps targeting older levels are blocked from being updated or newly published.
Almost always simply a maintenance gap: an app that hasn't been rebuilt against a current Android SDK in over a year, unrelated to any content issue.
"This app is not compliant with Play policy regarding target API level and cannot be published until you update targetSdkVersion, per the Target API Level requirement."