They need to UPGRADE the graphics, which pales in comparison to Space Engine.
Space engine just has to calculate and render celestial objects.
It has to move a camera to where you want to go.
It has some kind of a ship movement but it's more like a ship skin is pasted on your viewport.
It does this using your computer's available resources.
Elite has the same exact resources to work on. It doesn't magically buy new hardware for you.
On this same hardware, it has to do the procedural generation constantly because everything you see is generated as you see it and only while you see it.
It has to spawn NPCs, run their AI, know and update their positions, what ever they do, all the while they are alive in your instance.
It has to run your ship, according to your input using the flight model. It needs to detect collision between moving objects constantly. Their movements must be realistic after they hit some other moving thing.
It has to keep tabs on other statistics like your velocity, power consumption.
It has to constantly communicate to the server about what you are doing.
It has to do a million other things I can't think of right now.
All in the same hardware which is your computer.
Space Engine has some better visuals, OK.