It never fails lately. We actually get a movie that's a new story, instead of a rehash or continuation of a venerable tale. And people immediately start piling on, pointing out all the stuff in it that's been done before. But just because something contains story elements we've seen before doesn't mean it can't be new.
We saw this with Pacific Rim. They made big-budget action movie that wasn't based on a toy or cartoon from the 1980s, and tons of people couldn't help calling it a rip-off of Transformers mashed up with Godzilla, as if that made it less cool somehow. And now we're seeing it with the upcoming Jupiter Ascending, which is getting dinged everywhere for having a "chosen one" trope — when actually, it's more like the "lost heir to the throne" trope anyway.
Even when a movie gleefully steals from everything it can get its grubby mitts on, as in the case of James Cameron's Avatar, that doesn't necessarily make it any less of an "original" story. Cameron may have admitted Avatar is basically Dances With Wolves in space, but he still came up with a cool new world (including the telepathic fiber-optic connection between people and creatures) and the neat plot device of a human occupying a genetically engineered alien body. Plus there was still no existing Avatar fanbase saying "if it doesn't have the big red dragon, I'm rioting."
(Side note: If you still haven't seen Edge of Tomorrow, which we fell into the habit of describing as "Groundhog Day with aliens," you should totally check it out. Because it rocks.)
In fact, the classic example of a brand new property that stole everything that wasn't nailed down is the original Star Wars — and that didn't stop us all from loving it or from being excited for The Force Awakens. (Which will no doubt rehash a lot of stuff from A New Hope that was already rehashed from The Hidden Fortress.)
Plus Harry Potter.
Here's the thing: There's nothing wrong with tropes. It's all in how you use them. Sure, some tropes are overused, and used in lazy, repetitive ways. We've certainly had some fun with listing some tropes that we feel we see too often, but even in those cases there's always a possibility someone could breathe new life into them.
But also, there's a difference between a broad story element like "giant robots," and a trope like "the keys to a random car are always behind the sunshade." Those are both tropes, sort of, but only the latter is a lazy shortcut that everybody seems to use lately. The "he's standing right behind me, isn't he" gag is pretty much the same every single time you see it. Whereas "giant robots" could be a whole range of things.
I don't want to live in a world where we decide that we've had enough giant robots. Or where creators decide they shouldn't do a story about someone doing heroic things, because we've somehow gotten enough heroism. I don't even want to live in a world where creators obsessively self-censor to try and avoid doing gags that have been done too many times. Just try and put a new spin on them.
There's a certain gleeful mastery in identifying tropes, as if you've tamed a narrative through the power of taxonomy. (I've certainly engaged in that practice in the past myself, and will probably do so again in the near future.) But these things are just trappings. In any story worth its salt, they're not the heart of the story — in the case of Pacific Rim, it's the story of Raleigh and Mako getting past their damage and learning to "drift" together so they can kick some Kaiju butt, not just "hey giant robots and monsters, whoo."
It's like categorizing movies by the hair color of the people in them. It tells you something, but doesn't really get at the experience of the story in any meaningful sense.
Nobody would watch The Hidden Fortress and Star Wars back to back and think they'd seen the exact same movie twice. It's certainly not the same as watching a movie and then a remake of that movie, in which a lot of care is taken to tell the same story with a lot of the same elements in the same arrangement.
And an "original" movie (or book, or TV show, or comic) with shopworn elements is still different, in a few essential ways, from a straight-up remake or sequel/prequel/sidequel.
When someone decides to make a new Planet of the Apes or Teenage Mutant Ninja Turtles movie, they're thinking of things like brand recognition, and merchandising, and an existing fanbase who can at least help launch a new film. This helps shape everything about the project, which is bound to be at least somewhat in dialogue with audiences' expectations.
In the best-case scenario, you get something like Rise of the Planet of the Apes, which tells a wholly original story about animal experimentation and unintended consequences while still connecting up with the original Apes movies. In the worst-case scenario, you get Tim Burton's Planet of the Apes, which attempts to retell the story of the 1968 movie in a hamfisted manner, with dumb in-jokes like having Charlton Heston show up and say the "Damn them all to hell" line again, and an obligatory twist ending.
But when you have a brand new property, it's a much bigger risk, and there's conversely a lot more freedom. Even if you can pitch it as "Gone With The Wind in space."
And telling new stories — or adapting books and comics that have never been adapted before — is still important, for a few reasons. It lets people create the next Star Trek or Lord of the Rings, and tell stories without worrying about whether "people want to hear someone say that one famous line." That kind of newness lets people have more diversity, and different points of view, than if they're trying to update something created in the 1960s or 1970s.
But also? One of the main reasons why we love a new mythos is because creators get to take a much-loved trope, like "the chosen one" or "huge fucking robots," and do their own thing with it. Repurposing and reinventing these tropes is one of the main benefits of these new ventures, and we shouldn't deny them that awesome power.