As a brand new player to Discovery, I'm sure that my feedback will probably be different from a lot of other people. But the first two things that pop into my head are (1) Environmental storytelling, and (2) hyperconnectivity.
One of the first bits of environmental storytelling I discovered in 5.0 was Kepler being...gone. Or at least gone in the sense that I remembered from 20 years ago. After digging a bit in the forums I found that this was a feature and not a bug. While things like that can feel punishing for newer players, they help drive home the idea that space is dangerous and constantly influx.
Not necessarily related to hazards specifically, but just wrecks and various objects placed in out of the way systems to discover is also just a lot of fun. There doesn't necessarily need to be any direct explanation, because sometimes the meaning the player adds to the experience itself can be just as rewarding.
Hyperconnectivity - I don't necessarily think that everything should be connected and easy for all players to get too. But I like the idea of alternate paths/hidden jump holes/etc that can lead to faster or more varied playstyles if you know the game's secrets.
