More Words, Deeper Hole

You're correct - I remember multiple scenes on board the ships heading to Sky's Edge, and so I misremembered them as generation ships - wow, it's odd to realize it's been 19 years since I read it. However, while there were definitely problems, the sort-of generation ships (since the inhabitants were exceedingly long lived) in Reynolds' On the Steel Breeze. also reached their destination. Also, while it was a bizarre novel clearly based on Marshall Savage's nonsense futurism in his The Millennial Project Ken MacLeod's Learning the World is about and entire society of people who are immortals that found new colonies via generation ships.

I think as a general rule novels where the inhabitants of the generation ship or ships are immortal or at least very long lived tend to be filled with notably less doom.