and marvel HAS failed (theyve put out a good amt of crap IMO) it just that at this point, it doesnt even matter. Those movies already advanced the major narrative and build up of Infinty war, which is what its all been leading up to. (and still made disney a profit to boot, so they dont have anything to be mad about).
It's like doing a big comic book crossover like Infinite Crisis or Secret Wars, and some issues or tie-ins not being as good as others. You can tune in or not, but the story continues, and those movies/issues are there to catch you up if you choose.
They mastered that style with big budget flicks. Its impressive.