A bit late here. But I still have to comment the OP: Everything you write is true from your point of view. You look at all the extrinsic rewards and all of them are lacking. And honestly, for the game to remain plausible in a multiplayer environment, most of them have to stay that way.
Just like you can't usually become a king in a MMO, no matter how many saves-the-world quests you do. You can't have every player to be a king. So also in ED, no matter what you do and how many credits you make, you always will be one pilot in one ship. Changing this rule would create a completely new game, where piloting would just be a mere stepping stone to success. I wouldn't want that.
Now that we have extrinsic rewards covered, let's look at the intrinsic reward. The most important one wasn't mentioned: fun. It's the very one reason I still play. You can make a long list of negatives. It's very easy. But show me one other game released in the last decade, which gives the same feeling of piloting a spaceship. Not a space taxi, not a on-rails space train, not a pure arcade space-flyer, but something which actually feels like a spaceship.
This is why I am stuck here. There's so much to complain about, from missions and credits over exploration and power play to the fiasco engineers were and the pile of biowaste they still are after lots of fixing. But there's also to see the fine line they found between arcade-enough gameplay to allow mundane people to still operate the spaceships, while having enough simulation-like elements to make it feel like more than an arcade game. Not to forget the great sound work, which contributes a lot to how the game feels.
So for me it really boils down to this: if you enjoy the activity of flying these spaceships, with the feeling of being an future-simulation and accept a few gaps here and there, for accessibility reasons, the game is awesome. All the mentioned negatives can be worked around. If the flying itself is no fun for you, then you better move on. The extrinsic rewards are weak and will stay that way.
This. Star Forge, the entire flight modes (supercruise, etc.) the optical view of the Galaxy/Star Systems and so on, this is the reason I will stay with this game, and just pause it (as I am doing now) if I have no motivation. And motivation is killed easily with this game. Just a look at the grind walls you have to cross just to be 'allowed' to enjoy some content.
But I think I will continue to play.
I think, the problem with ED is, that they have developed a truly remarkable 'Galaxy and Space Flight Simulator'. But only flying around will not keep interest for a long time, so they tacked on a bit of MMO game play. And 'tacked on' it is. To a truly exceptional Space Simulator they gave totally inept world play and after years did not manage to make it better. I suspect, that the game engine does just not give itself to real game play, so NPCs are remarkably dumb and feel dead. There seems no scripting (as in scripts, easily tested and changed), only configuration tables with limited possibilities. True, I do not know that, but it looks like this, because some of the bugs should be easily fixed - but not when every fix means changing the core games code itself.
The entire world feels dead and boring. There are 1000s of factions with no reason, no story, no intent, no targets or objectives going mechanically through the BGS 'modes'. Even the 'dangerous aliens' are completely boring, and since you have to spend weeks of grind to just get the weapons to fight them, many avoid this 'content'.
There could be so many meaningful Missions. We do not need heroes, and they are not really possible in a MMO. And they tried to make nice Missions - but most of them do not work as intended, are buggy and better avoided. There are distress calls, with distressed pilots which just fly away without a word, if you help. And to help you need 3(!!!) full slots, for a cargo bay (limpets) and two limpet controllers (fuel and repair). Can be done with big and expensive ships, but why would I do this? Or you arrive in a system and are interdicted by security forces, and if you submit (because you are clean), they fly around like idiots, saying and doing just nothing.
Everything which goes a bit beyond the pure space simulation is hidden behind walls of grind, the Engineers, the Guardian components, all of it. Grind for days on end to be 'allowed' to use - just the game. So better only do the space simulation, this is at least a bit of fun, until you run into stop gaps, like jump range or other things, or you want to try out other things than exploring - you immediately hit a grind wall and have to cross it or give up.
The only thing that saves this train wreck of a game is the fact, that the core of the game, the space simulation is healthy and unparalleled at this time.
