I also have the same bad vibe with discourse.

For me the issue is that there's too much white space. I find the website uncomfortable to look at because the screen is mostly white and very little anything is visible.

I would liken it to the effect of being in a room with a very tall ceiling, it feels intimidating. This is why they built churches with high ceilings.

The website also gives me vibes of being a question and answer site like stack exchange, rather than a community.