I think a few things make the game easy :
Nav beacons -> Bounty hunters ghettos -> easy bounty camping, easy money. Just like roaming for special deals in your usual supermarket.
USS -> the way to tell the game you're bored and would like to have something happen (not taking into account the occasional easy-to-evade interdiction - pretty rare when you don't have a bounty on your head) - You want to be attacked by pirates or to get scanned and fined by authorities for your illegal cargo ? Just drop into an USS ! Otherwise, everything is safe : nothing happens if you don't ask for it. And as if it wasn't easy enough you can find easy money there too.
Getting to your destination -> Dropping out of supercruise so close from stations makes trading a no danger/no cost activity. Making ships dropping farther and triggering events/encounters during this part of the travel could make things a lot more interesting.
Only way I've found to make the game harder is to follow a bunch of strict self-restrictions (wipe save on death, only making business on piracy, no trade except blackmarket, restricting missions for specific faction type, no nav beacon camping, and no USS inspection out of missions goals). Like that, it starts to be challenging : when you have to sell a gun to pay the repair bill, each credit earned is really appreciated.