By thinking only about the similar aspect between the two games, that is trucking -space trucking/trading, let's see why is Euro Truck more successful, and what could ED learn from it:
In Elite for maximum trading profit, you find a good route with a few goods, with as few jumps as possible. So you load up on goods, take off, be careful not to hit something when going out, then jump, target the next station, wait to get close enough mostly by looking at a distant circle, checking your speed and distance the same way everytime, you exit supercruise, dock, sell product, buy next product, and repeat. Except the occasional interdiction, there is no variation to this formula.
In Euro Truck 2 you earn money with missions. These missions are randomized, but based on your experience and qualifications. And reward increases the bigger the driving challenge is, some missions being emergency transport missions, and so you have to manage your character's sleep carefully, and drive without serious accidents. Others are with fragile cargo, being heavily sanctioned for any damage to your merchandise, some are simply long distance trips from one part of Europe to the other. Its satisfying when you finish such challenging and diverse missions. And this is only the gameplay aspect, ignoring that you have some nice sights on the way.
I think Elite could match this system with an improved mission system, maybe similar in some way with Euro Truck, at least regarding trading.