The arc can be gracefully executed, but the truth is that the vast majority of villains wind up being disposable.
Naysayers will have their own arguments against, but to understand the accomplishment that Thanos is in the Marvel Cinematic Universe it helps to juxtapose his journey as compared to the general arc that is played out with villains not only in Marvel movies, but the vast majority of superhero blockbusters.
With the franchise on the whole primarily centered on heroes, there is a natural inclination for the films to treat the various antagonists we’ve seen as one-offs – serving the purpose of not only being an interesting and compelling foe, but also to highlight certain emotional and/or physical flaws that exist within the protagonist at the time of their showdown.