I applaud your optimism. And you're right. The design of the fediverse encourages these properties. But there are also other dynamics at play.
I wouldn't describe Lemmy as an intellectual place. It's more a cross-sectional take on society. It's a diverse place of common folks, a few nerds, people posting the news, sharing memes or asking questions...
It depends a bit on the specific community. Some have nice people and active conversation, some don't. Especially niche topics are a mixed bag. We're just 50.000 active users so that means for some smaller hobbies you can't really get a conversation going. But you included some broad topics. I'm sure some of them work well here.
!technology regularly has good posts. Debate and politics work very well all across the platform... I'm not really an expert on the communities here, I hope other people can give good recommendations. Art, literature and ecology also have healthy communities. Sometimes entire instaces dedicated to it.
I think if you're willing to share this place with a diverse group of people, you can get happy here.