Of all the things young people could have latched onto, it's the decade of the great recession almost no place on earth really recovered from, a head bozo in the US that's somehow popular but turned the world into his personal drone playground, while the empire continued as it did.
It was the decade every social movement failed in, and mostly retreated back to moralistic forms of liberalism, just as every equally moralistic right wing reaction grew exponentially, leading to the current issues.
It was the decade climate change was decided to be fixed through a bunch of treaties worth less than the paper they were written on.
It was the decade of the start of the return of the malaise of collapsing empires. Poverty, hunger, climate change caused disasters. War had not went away, but resistance to it did.
Plus, pop culture (the thing most of the nostalgia is directed to - the eternal "It's Christmas ~~1996~~ 2013 and my parents got me ~~a Nintendo 64~~ the new Call of Duty" of obnoxious liberals) sucked ass.
The 2010s had very few things going for it culturally. Some good video games, a good movie here and there. Frutiger Aero? That was kinda cool right? But overall? The 2010s sucked. I was an angsty teen in most of the 2010s, and so naturally I have a bias against that time period. I hated the fashion choices, the uggs, the white woman fallcore aesthetic, curly moustaches, gross. The pop music? Wack. Awful. Mumford and sons were a poison on this earth. Imagine dragon? Eeessshhh. It's like the one decade the Mormons ate good in lol.
Stomp and Holler, an abomination of a music genre. (maybe there's good examples around, but the bands that got big sucked ass)