However, that is absolutely not true of Destiny. The Strikes, Dailies, Weekly heroic/Nightfall, Bounties, Exotic weapon quests, and even the special 2 week long event are all made up of the exact same content you did while leveling. You even sit through all the same cut scenes and dialogue. The enemy abilities and behaviors never change, they don't even bother to rename or recolor them. They apply "modifiers" but those are mostly about "I'll shoot these guys with my Fire rifle instead of my Arc rifle this week."
Yes, I'll agree with you. The Strikes/Dailies/Weeklies are repeated content. But that's just things you do, checkboxes you tick during the week while waiting for the raid timers to reset to do them again. Doing PvP (either in Destiny or any multiplayer oriented FPS) and grinding reputation (be it in Destiny or in any MMO) is quite literally the same thing. People prestige 5 times in CoD, and they're technically just doing the same content over and over again.
The Strikes are nice equivalents of "Dungeons" on MMOs: An easier encounter you do with less people to get items (and, in Destiny's case, grind reputation/strange coins to exchange for items) while you wait for the raid timers to reset. And since they're easier, you don't need your core group of friends to do them with, which is why they have matchmaking.
The environment art is all recycled and most of the bosses are just oversized versions of regular creatures; Atheon may be the only exception. Even some of the interesting new mechanics like the Relic and syncing are constantly reused across the encounters.
The environment will most certainly be re-used: This is not WOW, where the environment is a 6 polygon model with low res textures applied to it. Personally, I would expect the DLC raids to be different in that aspect as well, along with new enemies inside the existing factions - most of the current enemies are just palette swaps of old enemies, but I have a feeling we will only get new bosses - Again, just like PSO.
The repetition of the new content/gameplay mechanics you pointed out is, in my opinion, one of the great things about the Raids in destiny:
When you first go into the raid, you have to protect 3 pillars and let them open to create a tower that will open the portal to the raid - that's unique content not shown anywhere in the game (one could argue this is just capturing the flag/king of the hill, but bear with me).
On the first Boss encounter, you're Protecting Confluxes, killing oracles before they mark you and kill you and cleansing yourself with the relic (which teaches you the concept of buffs and debuffs), which is also unique content to the game (one could argue that this is not new content when taking into consideration other games, but still).
You're going to point out that all three of those mechanics is re-used in the final boss, and I think that's genius of them. Imagine doing this for the first time. You're learning every set mechanic individually, and at the end, you have to apply all that knowledge from the 3 different parts of the game to kill the final boss (there's no excuse for the Gorgon Maze, that's just annoying, but so was the maze in the end of Revenge of Shinobi for the Genesis, and nobody was raising pitchforks and setting churches on fire because of it back then).
That's a very nice mechanic loop. You learn different new mechanics you never seen before, you hone them in, you apply them all together in the last boss.
Don't get me wrong: Repetition is the base of MMOs in general (And PSO, and Destiny, and Diablo...) You might not like it, and you don't have to, but that's what grinding is all about. If you deconstruct everything, everything is always the same. That's why the saying "MMOs are all the same, you just point and click at somebody until they die" exists. It's not wrong, it's all repetition. How it's presented to you and how you do it is the different part. And in that aspect, Destiny seems like a great game (I only played the Beta and i've been following a group of friends playing the game/talking about it/reading about it/watching streams, mostly).