EU themes in Serbian cinema are reflection of EU subsidies for Serbian films. Serbia has relatively small domestic market and it is very diificult for a film to be commercially viable. Many film makers take the easy route of taking money from EU or Serbian government and adapt content of their films according to their financiers' agenda.
This issue is even more noticeable in Croatia, which is a smaller country with smaller domestic market and less ability for commercial or audience-friendly content to slip through.