Same issue here. It seems most users prefer mobile apps to browser lemmy as many people use wefwef/voyager, which for me, it renders the thumbnails too big and it's a huge waste of space when used in standard browser.

I found this interface called photon which renders the thumbnails using a decent size but I think it's still in beta and it lacks some functionality like sorting the answers.

I'm on a more than usual wide screen so I just zoom the page

https://alexandrite.app is a great interface for browser viewing