I can see why, but that’s a pretty big generalization imo.

Serbia isn’t some hive mind - people have very different views depending on age, background, etc. Yeah, you’ll find nationalists (like anywhere), but saying “most people” I think like that is a stretch.

On Muslims - it’s more complicated than that. Serbia has its own domestic Muslim population and people live together normally day to day. There are occasional tensions on both sides, mostly leftover from the 90s wars, but boiling it down to “people don’t like Muslims” is just oversimplifying. On one hand Serbia was occupied by a Muslim empire for hundreds of years, so there is some resentment there, on the other hand Yugoslavia was very friendly with many Muslim states, Belgrade in the 70s was a hub for Arab students and vice versa many Serbian companies did construction work in Arab states, support for Palestine is generally large...so there's both sides.

As for Putin/Russia - some people are more vocally rusophile because of history (NATO bombing, Kosovo, that whole context), but it’s not like everyone is blindly pro-Russia. Simping for a foreign power is unfortunately a thing in the Balkans, like there is a subset of Albanians that will be pro-USA even when Trump does stupid things, or Bosniaks that are pro-Turkey and supporting Erdogan even when most of the Turks in Turkey don't - similarly, there is a subset of Serbs that is pro-Russian no matter what. However plenty of people are pro-EU, while the majority just doesn't care much either way.

So yeah, there’s a bit of truth in what you’re saying, but the way you framed it makes it sound way more one-dimensional than it actually is.