I'm going to assume that readers of this review have read other reviews that explain the objectives and mechanics of this game in greater detail, and stick just making comparisons to the original Destiny game.
In a nutshell:
The gameplay feels identical with regard to control response, button layout, etc.
The storyline of the game is much easier to understand and follow in D2 than in D1.
The visuals in D2 are even richer and more varied than in D1, which IMO had great visuals to begin with.
A lot of the Player vs Enemy combat sequences seem to have more enemies attacking at any given time, with more waves of enemies to fight, resulting in much longer battles and more player "deaths". Not better or worse than D1, just different.
Without giving away any spoiler details, I'll just say that the one Raid currently available is more similar in length and complexity to Crota's End (meaning: shorter and less complex) than to the other three raids in D1. Up to you whether you think that's good or bad, or irrelevant. The Raid has a lot of fun parts that require a lot of interaction within the team, overall I give it a thumbs-up.
The one area of the game I am not thrilled with at this point is the "loot system". This is actually two separate issues:
1) As anyone familiar with the game knows, playing the game rewards you with "loot": gear that increases your Light level, which increases your character's ability to inflict and withstand damage. The problem is, in D2, once you get to about 270 light (out of a possible 350), most of the loot you receive gives you gear that is BELOW the Light level you are already at. To be fair, I haven't done a lot of research on YouTube, Reddit or elsewhere yet to see if there are more effective ways to level up. But as of now, it seems like grinding hours of Strikes and Crucible in D2 will not raise my light significantly.
2) the Loot System has gotten more complicated. In addition to weapons, armor, ships, sparrows, emblems and shaders, loot now includes weapon and armor mods, each of which can be applied to a single piece of gear a single time. Shaders can now be applied to weapons and ships, in addition to armor, but each shader is a single-use item, and can only be applied to a single piece of gear. After hours of grinding, you end up with a much larger and more complex inventory of items to sort through. OK if you're a dedicated gamer, Not so appealing to the casual gamer.
On the overall i really enjoy this game, but unless i find ways of raising my light level more efficiently so that I have a hope of remaining competitive in events where light level is a major factor, this game might not hold my interest for three years like D1 did.