I'm pretty old so I could go on for days about cancelled shows from the 70's right through to now. But just sticking to recent times, two shows that were cancelled after only one season that really deserved to keep going:
1) Ascension - alternate history / sci-fi 2014 series on SyFy about a group of people who believe they're ~30 years into a multi-generational starship journey to a distant star, but in reality they're part of a secret underground experiment very much still on Earth, and being monitored the whole time.
2) 1899 - Netflix show from 2022 made by the same people who made "Dark." Set on a German ocean liner in (you guessed it) 1899, the crew and passengers deal with a bunch of spooky supernatural shit, and then at the end of the last episode you find out they're actually living all this while in suspended animation on a spaceship. What happens next??? We'll never know.