Ok, here are my thoughts. First off, I do not care what people think as I did not buy Destiny 1 and will likely not buy Destiny 2. As for why people think Destiny 2 looks like an expansion, a lot of the bolded from the quote above could be patched into the game, like many games that rework mechanics/systems as the game ages. The italicized from the quote above could easily be added to a game in an expansion.
Now, plenty of people will say that yes many of those things could be patched/added to destiny one but so could a lot of stuff that is in sequels! I understand and agree with that point, but I think the main problem with that argument is that Bungie sold Destiny as being a 10 year game so they sort of expect a continuously updated game (like WoW) rather than a brand new game that does not allow for them to carry their character over. Sure, if Destiny existed on a previous gen, where patching was not that common (especially large patches), I could understand the need for a sequel but with the current console generation all of this could easily be patches/content additions to Destiny 1.
Now, if you still argue that Bungie still has the right to release a new game ok, but again, many people were expecting a 10 year game and being told that a sequel is coming caused many to think this meant a big change in the general format of the game to more closely resemble what Bungie initially promised.
Basically, I understand the frustration of ardent destiny fans that say people are being harsh on the game. That being said, Bungie initally pitched Destiny as a 10 year game, so people hoped for something that could be continuously updated, but then when they announced that the sequel would not allow you to carry over your character they expected something drastically different than the current game and were disappointed when the sequel looked pretty similar to the first game in terms of structure.
That is my take anyway. Not saying I am necessarily right.
I stopped reading