Well, the Buddhists are more optimistic than that! They have lots of techniques and ways of thinking to reduce suffering. I recommend reading up on their life philosophy, they’re far from nihilists.
The main doctrine of Buddhism is that eternal bliss is possible, how is that not optimistic? I'm a Jodo Shinshu Pure Land Buddhist and as far as I can tell all Buddhists believe in this, it's the third noble truth after all.
To me it seems more optimistic to think that our current life is somehow limited and flawed and that a mind and experience beyond it is possible (Buddhahood) than to think that it's not possible and we are stuck as limited suffering beings.
