If the pilot is wrong you hope the copilot or someone else on the crew picks up on the error and corrects it. If they’re both wrong, or if they don’t feel empowered to challenge the pilot like in Korean Air 801, everyone is usually fucked.
ATC doesn’t have the kind of situational awareness or manpower to fix these kinds of problems the vast majority of the time. It only seems like they could have done something after the fact when the disaster has already happened and hindsight activates.
Like the GP said, ATC second guessing pilots is a really, really bad idea. A few incidents doesn’t change that.
That specific incident resulted in a lot of changes to the rulebook and some very specific notes about training in terms of cultural differences.