Games without good visuals/design can sell, but there's not a ton of games out there with ugly/sloppy graphics that become hits (they do exist, sometimes it's kind of the point of the game).
So if you don't place a high priority on aesthetics, you're taking a risk in your game not finding an audience. And I'm saying this as someone who designs games with a mechanics-first mindset.
The board game industry is very aware of this, and very few publishers skimp on game aesthetics nowadays.
When there's hundreds of thousands of both great and aesthetically pleasing games out there people could be playing, why should they waste time playing a game that doesn't look good to them?
