At this point, the franchise needs to grow beyond Sparrow or else the franchise is dead. Rather than create a whole new franchise under a "reboot" it's wiser to keep the brand identity going and steer the ship in a different direction.
Disney wants that female pirate character of "Red" they brought into the rides to replace the Auction scene to take off so badly. People blame whatever -ism they want when things don't go how they envision, but I think if it's good enough, anything can take off. We'll see if this ends up being good enough.