Basic things added:
Horizons brought landable planets (any planet or moon without an atmosphere can be landed on, some are real neat).
Wings are in the game, as is multicrew, but both are subject to the networking going right. Others would have advice on it if you're interested.
The VR is great, by the way, and I can't recommend it highly enough. They added things that are fun but don't get used like CQC (a separate combat game mode in small ships and nice environments; the environments made their way into the real game in the form of "Installations" and maybe some other stuff), and Powerplay has a devoted following but the fun of it seems super subjective. There's also 2 alien races now; the Guardians and the classic Thargoids.
The Guardians are extinct, but you can explore their ruins and do some (grindy) stuff to unlock different modules that are helpful; in particular the FSD Booster (which can add 10ly to your ship and fits in an optional internal) and different weapons to fight the Thargoids with. The Thargoids are a cool creation, and opinions will differ on how they've been implemented but things such as their design, sound, the challenge, their base found on planets, all of those are pretty universally praised. The Thargoids and Hu-mans are at war and the Thargoids have attacked a bunch of stations, so a good-sized amount of the bubble is in a state of repair and you can rescue passengers from recently attacked stations.
Passenger missions are in the game, though I don't know what the original plan was for them so I can't say if they fulfilled the full stated intentions.
Ship-launched fighters are a favourite of mine; a few ships can equip the fighter hangar and all of the SLFs are really fun to fly and helpful in combat. You hire NPC crew to fly them if ya like, or fly them yourself and your crew flies the mothership.
They overhauled mining and exploration for the last chapter of the Beyond series of updates, introducing "deep core mining" where ya explode certain rocks to get the goodies inside for lots of money, and added a Full Spectrum Scanner and probes to map planets with. I think both are much more engaging now, but there's a range of opinions (at least on the FSS and exploration stuff). They also added strange phenomena scattered through the Milky Way, which can be cool.
The Engineers were a part of the Horizons update; they totally changed the balance of the game and what determines a maxed out ship. You unlock the engineers and then they can work on your modules (different engineers able to work on different things), making your ship much faster, jump much further, weapons mega powerful, much lighter, etc etc. It changed things a lot and hasn't always been properly balanced, but they did a mini-overhaul of engineering for the first chapter of the Beyond updates which made engineering easier and less annoying to take part in (I won't go into detail how annoying it used to be, but it's easier now).
If ya wanna PVP, you'll need to be engineered, just to warn ya. If you're in Open, many ships will be much faster and more powerful than ya may remember. Money is easier than ever to make though, so if ya die you'll be able to recover the lost cash quickly.
"Beyond" added the ability to rob megaships (lotsa megaships all over now, some can be landed on) and installations, and also a newish thing called "Scenarios" were added. They're fun and voice acted "spontaneous" events, like if you're at a megaship and then pirates attack and the megaship will ask for your help or you can help the pirates rob the ship. Or if you're at a CZ and your side asks you to kill some war reporters or a general, or send the capitol ship packin', stuff like that. Also can be found at signal sources, like someone needing fuel or food.
Gathering data and materials is important for engineering (data and materials makes up the ingredients for the engineering recipes) and for synthesis; you can synthesize ammo, limpets, repair your SRV, etc. Some data and materials are a pain to collect but there's various tricks to speed the process up that you'll learn if ya get into it.
There's been various QOL updates along the way; you can plot up to 20k ly with the Galaxy Map now, you can store 120 modules, transfer ships and modules for a fee (and wait time), lotsa new ships that're cool, ummm what else... I'm going off the top of my head for most of this. It's been slower than most people like.
There's a second populated bubble of humanity about 21k ly away; it's called "Colonia". It's much smaller than the regular Bubble (which has also grown) but is located in a nebula and seems like a cool place.
There was a recent leak (so who knows if it's real) that says the 2020 update (called the biggest ever by Frontier) will have the long awaited Space Legs and the somewhat surprising addition of player bases. Again, we don't know if that's real and Frontier hasn't talked about the update except to say a while ago that it'll cost money like Horizons did and that it'll begin a new era of Elite. If ya got the Lifetime Expansion Pass then you're covered.
We don't have word on Atmospheric Planet landings, or what form Space Legs will be if it is indeed gonna be added (so no knowledge of ship boardings, FPS action, walking around stations, etc etc).
We do have player avatars, and the player creation tool is pretty good. They also sell cosmetics for the ships and clothes for your avatar and other stuff like that.
This year is much smaller updates; they added to the new player experience with an update a few months ago (they created a New Player Safe Zone and changed the UI a bit), and the next update is meant to be along the same lines (no word otherwise from Frontier yet, but it'll be in a month or two or so), and two more 2019 updates after that and we got no idea what it'll be. And the big ol' 2020 update is slated for the second half of 2020, so it could be X-mas if it ain't delayed (no reason to think it's delayed or anything, just that it may be a while).
Squadrons were added, and player owned fleet carrier ships were meant to be added in the last chapter of Beyond but they got delayed. We don't know when they'll be in the game. I don't have experience with Squadrons to tell ya how functional they are, but people seem to use it. They also were meant to do an overhaul of ice planets and make them look real fancy, but that was delayed as well. They did do a visual improvement to the surfaces of the landable planets for the first chapter in Beyond, and I think it looks much better than it did prior.
That might be about it! If ya look up player guides, for most stuff (especially engineering) be careful following some guides that pre-dates 3.0. Some stuff is still relevant, but the details of things change and old guides can steer ya wrong.
