Firstly, which developed countries (that don't have "cheat codes") haven't stagnated GDP-wise post 2008? AFAIK, most of them.
>a country that hasn’t climbed out of the middle income trap yet
Secondly, GDP growth as a number on it's own, is pretty useless, as it's not a 1:1 representation of quality of life increase for the average citizen. GPD can grow just from some billionaires moving trillions form one to another or from extracting wealth from your country and its citizens, that doesn't necessarily mean the average citizen gets a piece of that pie or gets to see better quality public services. It just feeds the "line goes up" crowd who see a country as a publicly listed corporation.
Thirdly, as a country, once you reach a certain level of development by plucking the lowest hanging fruits that have been tried and tested and know to work by former industrial powers, growth becomes much harder and more capital intensive, only accessible to countries that already have crazy money to spend in R&D and innovation in the newly developing high growth markets, like the US, UK, China, Netherlands, Switzerland, Scandinavia, etc. Everyone else is stuck waiting and playing catch-up for eternity, but that doesn't mean they live poor lives.
The GDP per capita of Zimbabwe grew 3x post-2008 while Slovakia has relatively stagnated, yet I know for sure in which one I'd prefer to be born in.
>calling it one of the most developed countries is stretching the facts beyond breaking
It's one of the most developed countries in the world when you look at how bad the whole world is doing right now, not just the US, Germany, Singapore or Australia, which have their own challenges when you zoom in on them and not just glance at the "line goes up" GPD numbers.