We have the knowledge from hindsight that WW1 was not, as everyone thought, the war to end all wars. There was worse to come, much worse.
There's not much that I don't like about the 1920's, the music, the fashions and the wonderful motor cars, but the rise of Hitler in that decade and what was to follow later, not for me thank you.
The 1970's, a decade of soaring inflation, political upheaval, and the erosion of democracy's prestige worldwide. It was also a decade of high fuel prices, they quadrupled here in the UK and we had long queues at every garage despite the almost daily price increases. The 1970's was also notorious for Watergate and Vietnam. No thank you to that decade too.