By and large, yes. Serbia has an aging population and especially older people (who constitute a large part of the current regime's voter base) are susceptible to this narrative of foreign powers trying to keep Serbia down. It's a tried and true authoritarian spin, persisting for decades in these areas. It doesn't help that historically, foreign powers were prone to aggressing against Serbia.

Younger people obviously don't fall for this (better informed, Internet-native), but they're more apathetic than anything. One cause for this is a lack of good alternative political options; the opposition is mainly people who've been in power before and were just not much better than what we have now.

If you could rally people behind an uncompromised, clean-slate political option you'd break the apathy, a critical mass of voters would emerge quickly and I believe Vucic and his cronies would fall in a heartbeat. But sadly nothing of the sort exists.