The main problem with DU at the moment imo is a lack of other gameplay loops other than just mining. So I have a few suggestions for things that should be added
Exploration Sites
Exploration sites would be locations scattered around space (mainly around planetary bodies) that you would have to scan down with a minigame. to do this you would fit a "probe Launcher" to your ship and you would be able to spot signatures up to 20 SU away from you to scan down, and once you do you get the location of the entrance to the site. once you reach the entrance, you are no longer able to be detected on radar so if people want to come kill you they have to scan down the site as well. In the site there would be locked containers floating in space left behind by whoever left the monoliths behind (to keep with the lore), which you would also have to unlock with a different minigame. The loot from these crates would have to be valuable and new, which leads to the next new gameplay loop.
Limited Run Schematics
All schematics other than T1 should become limited run schematics and not be sold on the market. This would mean that industry would become actual gameplay, as you would have to replenish the schematics in your machines whenever they run out, either by manually adding schematics to the schematic banks or from containers that the machines could draw from whenever they run out of runs on the current ones. The way to get these schematics would be to either find them in exploration sites, or through invention. For invention, you would get a schematic of the previous tier and put it in an "invention machine", select the desired output for schematics with multiple possible upgrades, and hit run. These invention runs would not have a 100% chance of success, and whether or not it succeeds it would consume the schematic it was given. Invention run success chances could be improved with special parts from exploration sites, and for T3+ invention you could add an extra item from exploration sites that would be necessary to attempt the run.
Feel free to critique this any way you want