Mine is Becky Chambers. I've just finished rereading all of her work, and it gave me the exact same feeling of hope I had the first time. Not groundbreaking, but soul-feeding.
China Mieville and Ursula Le Guin are both up there are authors who have written things that have felt momentous to read.
But I'm not sure either of them could edge out Terry Pratchett as the author whose work I've enjoyed going back to time and time again, having read most of Discworld at a more formative age probably helps too.
Who is your favourite author?
Mine is Becky Chambers. I've just finished rereading all of her work, and it gave me the exact same feeling of hope I had the first time. Not groundbreaking, but soul-feeding.