I've played many MMOs since the days of EQ and UO, and single player games as well, pure PvP FPS games and puzzle games, even Facebook based games(love Angry Birds), and they are all nothing but repeatedly doing the same things over and over, the context may or may not change, the target may or may not change, the graphics may or may not change, but you are just doing the game things over and over. Storyline is all that changes, and that's usually one of a handful of different stereotypical storylines with you as the hero or for a REAL change up, you as the villain!
SW:TOR and WoW, the difference is the setting, you are still doing the same things in both games, go kill X of this, go collect Y of that, go kill this boss. Storyline is different, the actual mechanics are different but it's the exact same thing. Same with LotRO or DDO or Scarlet Blade or 9 Dragons or Altantica Online, different games, different makers, different stories, same thing over and over again none the less.
And make no mistake, Elite Dangerous is an MMO, as an MMO is simply an online game played by a lot of people at the same time, a persistent world isn't even a requirement, nor is a quest system, or storyline.
There is no such thing as a classic MMO, it quite literally means Massively Multiplayer Online, that's it, and Elite Dangerous is exactly that. YOU are referring to games like EQ and UO and WoW, which are exactly as deep and engaging as Elite Dangerous to the vast majority of their playerbases. They are nothing but repeatedly doing the same things over and over again, only those others games have a storyline which is used to push the player around the game world and direct where they go and what they do at all times. Elite Dangerous has no such storyline pushing the players around, that is the only difference between them, it HAS a storyline, it tells you that storyline if you want it to, but it doesn't force you to follow that storyline in order to play the game as those other games do.
Doom, Quake, other FPS games of that type, exactly the same thing, there's a storyline that pushes you around the game world in a preset sequence, it's otherwise doing exactly the same things, killing the mobs put in front of you, over and over until you reach the end of the story, which is the end of the game. No more depth and engagement that Elite Dangerous, less really since you almost never have any options on those genre of games.
Skyrim, single player game that is storyline driven, it just has multiple storylines you can follow along the main one, and it has PG questing. And it has no more depth and engagement than Elite Dangerous does using that same PG questing system. Skyrim is one of those few games that gives you options, of a sort, but in the end, it's still just you doing the same things over and over again. The Witcher games are like that too, better story in my opinion at least, and the first one gave you very limited options and was pretty linear, the second was a bit better on allowing you 'freedom' but still linear, while the third gives you freedom to explore all you want..but the storyline is still how you actually progress through the game. GTV V, same thing, open world/sandbox I hear it called all the time, only, if you don't follow the storyline, you don't actually progress, and nothing you do outside of the storyline has any impact on the game world at all. You can go blow up the same cars and people on the same street over and over and over and over...yeah, that's so deep and engaging isn't it?
What most people consider depth is usually a storyline that draws them in, that's it, nothing more. That is not depth, it's a tool that's used to herd the player through a preset sequence of events and that's it. People LET it do that and call that depth and engaging game play, but in reality it's being forced to do what the game designers want you to do.
For others, at least from what they've posted on these forums on these types of threads, depth is making more ingame coin for whatever they are doing, that's it. They see no point in doing X for 500 creds but they'd consider it well worth their time and effort and deep and engaging to get 10000 creds for doing X.
Depth has different meanings to different people, which is funny but also makes sense, we're humans, we can't even all agree that killing each other in the name of whatever isn't something we should be doing, so what can you expect?
To me, personally, depth is things like the mechanics of the game, and Elite Dangerous has plenty of depth there. It's the ability of the game to draw me into the game world, which Elite Dangerous does very well. It's also the ability of the game to make me WANT to play it more, be that through goals the game sets or I set myself, which Elite Dangerous does very well, or because I just enjoy the game world setting, which again, Elite Dangerous does that. And these are all for ME, no one else, so for ME, Elite Dangerous has plenty of depth already. I don't need a justification for whatever I'm doing in the game, be it killing pirates or running cargo or data or mining or just flying around and looking at stuff(which I do a lot of), the game allows em to do those things or not as I see fit and it provides me the options via missions to do them for a reward that is not only game coin but also reputation and influence as well, so that if I so desire(and I do), I can play around with the BGS and change what factions are running what systems, cause them to grow and expand or stifle them until they stagnate and die out. Talk about depth, the BGS and factions has that in spades, but so many people ignore it totally. They say that depth means being able to have a real impact upon the game world, something that NO MMO out there actually does, and they totally ignore that you can do exactly that in Elite Dangerous, and it has a real and meaningful impact upon the game world, it's not just another title for killing the boss of a raid(who's been killed 203 times so far today). That's depth to them, getting a title for killing something that a few thousand other people will also kill every single day of the week, but being able to cause a faction of your choice to grow and expand to multiple systems, that's not depth, that's not leaving any mark on the game world.......