Why is our country worse at football than Croatia, which has a population of only 4.5 million?

‌Croatia has a population of only 4.5 million, which is only 1/10th of South Korea's.
Even if half the population of Seoul went all-in on football, it wouldn't even reach half of our country's population.
Even though Croatia is not a country that only plays football as a sport,
don't you think we fail to produce world-class football stars compared to Croatia and struggle with poor results in international competitions?