Every country has lots of struggles. There are a few European cities I would consider close to perfect but when leaving said cities things can become more difficult in the same country. Vienna and Copenhagen might be my two favorites. Rent is still fairly affordable in both cities especially given the available salaries. Both have great public transportation, lots of green spaces, good access to education and healthcare, and a healthy entertainment sector. Both countries are doing fairly decent overall. Denmark is probably ahead of Austria because Austria has a bigger right-wing. So by extension I would say Denmark might be as close as it gets.

Obviously there will be a few smaller towns that are even better but they are too small to consider.

When talking about a whole country a lot of it comes down to personal ranking on what you consider important. When leaving central & northern Europe the relative income drops significantly in most other nations. Which would matter for some as it affects the possibility of traveling, while for other it doesn't.
Many of the pacific island nations have a surprisingly high standard of living despite poverty being an issue. But even if you don't care about money and would rank the relaxed living there over the working culture in Europe there is another issue that affects some. Abortion is illegal in most of them, it's usually allowed for medical reasons, especially if the life of the pregnant woman is in danger. But for some the lack of access to abortion would totally dismiss these countries from consideration while others prefer them for it.
Singapore could rank very high but the fact that there is the death penalty for drug related crimes is a huge red flag for many. But again, others even agree with it.