Sure, lived there 15 years and obtained dual citizenship.

I've now lived long term in my third country, so I am certainly in a position to compare living in multiple countries. If we want to focus just on depression, it's a mixed bag.

Do Koreans work longer than other countries. Yes certainly. Statistics support that. Are they necessarily working 'harder'? Not always. It depends a lot job to job, company to company.

To me the biggest thing contributing to overwork is the lack of holidays. For the longest time most statutory/bank holidays were not given additional days off if they fell on the weekend. Combine that with most companies not just giving you 2-4 weeks that you can use whenever you want, and most people worked a lot with little down time. Most companies would have a bit of time off in the summer, but they'd all take it at the same time and the prices would sky rocket meaning it was hard to enjoy what little time off you had.

This is not universal though. I know some larger companies had programs where people got specific days of the month off in addition and some had other half days on top of that.

focus on collective and ignoring individual needs and problems

This is a tough one. While they certainly do that in Korea, and things are changing in that regard as they're acknowledging individualism more, it has certainly lead to a lot of efficiencies. As an example, to exchange a driver's license in Korea it takes about 30 minutes and costs $10-15. In the UK you need to send it away, it costs £45, and takes 3+ weeks for them to process. If there are any issues, like say someone at the DVLA told you that your license officially printed in both English and Korean didn't need a translation and then some jobsworth at the DVLA decided it did upon receipt, it has to be first sent back to you before you can go correct it.

For the most part bureaucratic stuff in Korea, while often talked about on the internet, is far easier to deal with, and much faster than it is in any of the other countries I've lived in. They also have a solid, central clearing house for making complaints about any organization in the country, government or private, and it can be done in just about any language.

The biggest issue I see contributing to poor quality of life is the density. Even when you have free time, you can't enjoy anything outside of your house there. Want to go to the part? so did 1500 other people. Want to check out the cherry blossoms? Sure thing. Tag along wit your 5000 neighbours. Hit up ikea? Sure hope you like walking through it shoulder to shoulder without the ability to actually look at anything.

The density also means that no really has the ability to spread out and relax. Everyone lives in apartments/condos. Very few have yards. Those are the real day to day negatives that drag people down. I worked in companies as a proper employee and managed people as well, and while it was tough at times, it would have been so much better if it was possible to really enjoy your life outside of that. People want to, but it's just very difficult in a small space with so many people.

Society is complex, visting a country is different from living there an extended period of time and even then even small geographical distances can result in huge changes in culture.

For example if you started in London and travelled the M4 to Bristol and carried on through Newport and then Cardiff. You would find dramatic differences in housing costs, religiousness, sports played (e.g. football to rugby), views on public transport, job market, jobs people work, education level, favourite drinks, marriage, etc..

You could spend 3 months basing yourself in any one of those locations and derive completely different views on what is wrong with the UK.

Which is why the OP brushed this off as nonsense. It also isn't uncommon for Americans to go somewhere and suggest it would be miles better if it was exactly like the USA, which is why you get the ad hominem.

It would be like a British Tourist suggesting they don't drink enough larger or accusing themof being savages for putting salt in tea

The author wasn't making a logical argument, so there's no need to address his "logic."

He's a tourist who spent some time in a foreign country, and came to some very sweeping, rash conclusions about an entire country's culture. It's shallow, judgmental, and tragically commonplace among self-centered tourists who think they can understand an entire culture after 2 weeks living in a hotel on someone else's dime. I am so done with the "white dude waxes philosophical about Asian country" trope.