Yeah, For All Mankind is a great show for people who are excited about this kind of stuff. It's an alternative-history fictional drama exploring "What if" the space race never ended.
I wanted to like it, and having some (reasonably-)big-budget visualization made of proposed rockets like Sea Dragon was great. But the (imo) awful dialog made the show unwatchable for me, and they did a lot of scientifically silly stuff like taking the Space Shuttle to the moon.
Yep. Highly enjoyed its Season 1, but I wished I never watched any further - it feels complete at this point and the later seasons destroy the impression. Kind of like with The Matrix.
Note: some people have an opposite opinion, that the interesting stuff starts at Season 3.
Agreed, Season 1 was by far the best. I'm re-watching the whole thing with my spouse and in some ways it's more fun the second time around (surely biased because of the shared experience).
Some shows are like that - I didn't think Star Trek Deep Space Nine was all that hot first time around, appreciated it much more years later on a rewatch (the supporting characters are awesome). Maybe in part it's adjusted expectations ;-).