I don't doubt that there is some degree of domestic favoratism—it would be surprising if there weren't any—but Korea was for years the last bastion of Internet Explorer because of government requirements, as opposed to Chrome, Firefox, or some special Korea-reskinned Chromium. iPhone has lots of market share despite Samsung.[1] Relevant to this discussion, Korean players going back to Starcraft a quarter century ago were and are well known for competing in and livestreaming mostly non Korean-developed videogames.

[1] Yes, I know about Apple being a Samsung customer

That's the counter-argument.

As they don't have competition from global products, they can deliver worse products and don't have the need to improve.

This can be seen in many markets with import restrictions/tarifs.