There's no guarantee that 2021 will be better. It's possible that the past 30-ish years were an anomaly of relative peace and prosperity. Consider the generation that lived through WWI, the great depression, and WWII.
That said, I'm thankful to have had the privilege of completing yet another orbit around the Sun on this tiny speck of a planet. Nothing but empathy for those who've lost lives, loved ones, and livelihoods -- I don't want to minimize their plight. We lost some friends (COVID and other), while others experienced job losses and economic hardship. As I'm sure is true for many here, our personal finances were a rollercoaster, but mostly worked out in the end. We sold our house and did a long distance move during the pandemic, which presented a bunch of unique difficulties, and we missed out on a bunch of "normal" life. I'm sad for my kids, a year seems like an eternity to them and they badly need real human interaction with other kids. However, the challenges of 2020 have produced growth, with increased patience and resilience. Above all, a much stronger sense of gratitude, that life itself and everything that comes along with it is a gift.
So I'm thankful for 2020, with all its ups and downs. And I look forward to 2021, whatever it happens to bring.