Like this person, I am quite liking Destiny's Year 2 expansion, The Taken King. I'm a quite non-hardcore gamer, and I actually haven't played very far into the new story material yet (I just finished the first mission on the Dreadnaught, a gigantic, eerie Hive ship orbiting Saturn, which is a new world in itself). But it feels like there's a tremendous amount to explore and do; it doesn't have the thin-ish quality of the original release or the first two expansions.
Many of the biggest improvements, which get only cursory mention in most reviews, actually aren't down to The Taken King itself, but the changes to the progression and quest systems. These changed with the 2.0 release, which landed a couple of days before the new content launched, and I actually had a really enjoyable time in that interval just replaying some of the old story missions with one of my less leveled-up characters.
To sum it up: the game does not push you to grind repetitively so much as it used to, and even in the existing content, there's more emphasis on story. It's as if they have more confidence in the depth of the game content and don't feel the need to pad it out with forced repetition.
They've completely changed the way leveling up and "Light" work: the cap for experience-based leveling is twice as high as it was, and Light is a parallel system rather than a thing that suddenly takes over after you hit the cap. Light is associated with all gear, not just the rarest kinds of gear. It's possible that once I get way past the level 40 cap, and things get more triggered by Light levels, I'll have to start grinding away again, but at least a lot of the game is accessible before you get there.
Also, they've vastly increased the number of bounties you can be working on at one time. These are little target achievements that give you experience points when you hit them. The increase in capacity means you can progress quite a lot just by completing them incidentally during normal play; targeted grinding on bounties is not as important as it used to be.
You also no longer need to go back to the game's hub areas to turn bounties in, which is a huge time-saver in itself.
On the other hand, they've organized both the existing and new content into multiple quest lines, with a narrative flow that does involve going back to the hub areas between missions to chat with NPC characters. They started doing this to a small degree in the Year 1 expansions, with the quests represented as bounty-like items that, frustratingly, took up already-scarce bounty slots. Now they are separate from bounties and have a multiple-page UI of their own, so it's possible to have many more quests going on at once. There are multiple quests running through the story main missions, but also quests having to do with skill development (and activating the highly touted new character subclasses), and some side quests that are more like enlarged bounties.
I actually like the interstitial bits where you have to go back and talk to your mission-giver, since it gives the characters more personality, and the game missions a greater sense of purpose, than they used to have. The Taken King takes it further, with more and more involved story cutscenes, featuring a whoooole lot of the voice of Nathan Fillion.
(Meanwhile, Peter Dinklage is gone, replaced even in the launch content by Nolan North, who, it was pointed out to me by a friend, is basically doing an American-accented C3PO. He takes some getting used to. I am in the minority who actually kind of liked Dinklage as Ghost, but I guess North is OK.)
A significant amount of what I'm doing now is actually playing through, not The Taken King proper, but the previous two expansions, The Dark Below and House of Wolves! I'd lost interest before, because way too much grinding seemed to be necessary to level up enough to make these missions playable. Now that's no longer true.
I've heard that people who aren't interested in buying the new expansion are upset that some old content just went away for them when 2.0 landed, and I can see why they'd be frustrated. I'm enjoying this, though; I think The Taken King ups the game's fun level quite a lot, and that's what's important.