It isn't easy to do something original in Hollywood. Hell, there's a reason why most of the biggest movies are sequels to successful franchises, reboots of successful franchises, or adapted from a franchise that's proven successful in a different medium.
However, while it is often safer (but never a sure-fire bet) to capitalise on a trend that's already up and running or to copy the formula of another studio, the big money comes from reinventing the wheel, and giving audiences something they haven't seen before or - in a lot of cases - something they didn't even know they wanted.
Obviously, that's easier said than done, as creating something original is hard enough, but creating something new that sparks a movie goer's imagination and gets them to buy a ticket is virtually impossible. The MCU makes it look easy, but there have been so many movies that have fallen on their own swords.