Virtually every country has its own unique nouns, idioms and slang ..this is not just an issue in Argentina. As a British guy who learnt Spanish in Buenos Aires whilst living there for 6 years, my experience is the complete opposite of what you have posted. I am pretty much fluent now and have had long and interesting conversations with many other Spanish speakers in numerous countries in South America, Mexico and Spain. I obviously grade my language to avoid using slang, lunfardo etc when conversing with non-Argentines but to suggest another Spanish speaker will not be able to understand you or think you're talking gibberish is nonsense

^