Well, I would beg to disagree. While the standard Serbian and standard Croatian are very similar, it's more of an artificial. Even when that was one language official, one part of ex country called it Serbo-Croatian, and other one Croato-Serbian, and the versions taught at school were similar, but not the same. There were some language constructs that were in this common language just because they were present in one, and not the other, so that Serbo-Croatian was a strange mix.

Not to mention dialects. Being a native south Serbian speaker, I had much better understanding of Macedonian and Bulgarian than those Croato-Serbian dialects spoken in the western or south Croatia.

I guess if it weren't for that political push to make Serbian and Croatian language the one language, those language would be much more different today than they are. Not to mention that simply choosing another Serbian dialect as standard Serbian, and another Croatian dialect dialect as standard Croatian would make those two languages unintelligible. Instead, it was a political choice to choose two most similar Serbian and Croatian dialect to be official standard language, and then enforce that at schools. I know that for example in southern Croatia people were forced to use standard Croato-Serbian at schools, and people in southern Serbia were, and still are forced to use Serbo-Croatian at schools, TV and all official institution.

Yes, language is a politics, and politics frequently molds languages in the direction it chooses. Orwell was not that far away with reality.

I would disagree as well. Most Slavic languages are much less closely related than Roman languages for example. I'm a native Bulgarian speaker and while I can catch some words when travelling in Serbia it's not that straightforward to understand others or to explain myself. I can understand people better in Croatia actually, which is kinda weird cause we don't share a common border. If I go to Poland, the gap becomes even wider. But for both the gap is significant. Grammar is different (e.g. inflections vs no inflections), pronunciation is different, hell even the alphabets are different.