Even in the most merit-based of situations, unless a person has the money/power to fund their own opportunities, an opportunity needs to be given to show off those skills. And the world very definitely is biased in who gets those opportunities. It's about class, race, who you know, wealth, gender, where you were able to go to school...etc.
I'd posit that this whole film is about the family using those skills to lift themselves out of poverty through opportunity and creating more opportunities for themselves the only way they see possible. I get that it isn't the way we'd like to see it happen in an ideal world but even the least underhanded position the family got, that of Ki-woo becoming a tutor, highlights just what they're up against.
Ki-woo only gets that opportunity because his friend (it's so often about having the right connections) presents this opportunity to Ki-woo. The only reason he's offering it to Ki-woo is because he wants to date the Park daughter he's tutoring and doesn't trust his university friends not to put the moves on her. He doesn't think Ki-woo is a threat on that front.
But even with the skills and even with his friend's recommendation, Ki-woo still needed to doctor up credentials/pose as a university student. They know that even if he had perfect English and the recommendation of their current tutor, a poor kid from the city wouldn't cut it for the Parks.
The way they infiltrate the Park household gets darker and darker but once there, they do have the skills to be successful.
This movie isn't about people with money being bad vs. people without money being good. If that's the message people want to see, they can see the also very entertaining Knives Out. This movie is a commentary on class and social status in general and what it does to people. The poor have a scarcity mindset. The rich become oblivious to the struggles of those who have less. It's kind of ugly all around.
There's a reason why the images we saw of Ki-woo's final plan to work hard, earn money and buy the house were shown to be a fantasy.
I believe it because the homeless man didn't kill the rich businessman. He killed the poor girl committing fraud and was then killed himself. The police are putting all their energy into trying to find Mr. Kim who killed the rich man.
BTW, earlier in the thread we were discussing how we'd react if we were Mr. Park and our son had passed out--I think he loses a little sympathy because, in all the chaos and alleged worry, he was still able to turn up his nose at Geun-sae's smell. That's what finally pushed Mr. Kim over the edge.