One of the things that sets the original apart from a lot of other open world survival craft games is that it was designed to be a single-player experience. Hopefully they can make it work well for both solo and co-op, but that's a tricky balance.
One thing I'd really like to see is for creatures to be able to damage structures, and to balance that by having defenses to protect those structures. Being able to throw together an invincible fortress in seconds made some of the dangerous areas a lot less threatening.
I do agree that the game's story/atmosphere should be designed for singleplayer first, since that's what drew a majority of people to the first game.
However, I think MP could still retain some sense of atmosphere as long as they have a good in game voice chat and keep it proximity based, like in Lethal Company.
It isn't scary at all for your teammate to tell you exactly where they just died, how, call out the leviathan heading your way, then continue with a joke they were making. But having a friendly conversation over the radio cut off by their violent death to horrors unknown could be scary, even if facing the unknown alone is fundamentally scarier.
I had the same feeling with planet crafter. After a while you learn to run around with just enough materials to build a room and a door and bam, the whole oxygen management mechanic is neutralized.