You need to grant Accessibility privileges under Accesibility Controlapane in System Preferences to AppleVNCServer which you can find under /System/Library/CoreServices/RemoteManagement/AppleVNCServer.bundle/Contents/MacOS/AppleVNCServer
Found from : https://apple.stackexchange.com/questions/339114/allowing-vnc-to-control-computer-under-10-14-mojave