While you were consumed by Roseanne's tweets and the ensuing backlash, something bigger happened in Hollywood this week. Netflix Inc. firmly established itself as the world's most valuable media company. Let that sink in: An 11-year-old app that charges $11 a month is worth more to investors than the legacy conglomerates that earn billions more from TV advertising, box-office hits and cable and internet packages. In fact, Netflix leapfrogged at least one traditional media giant in market value each year since 2015, when it became twice the size of Sumner Redstone's CBS Corp. Almost symbolically, that was the same year the elderly media magnate stopped participating in CBS's earnings calls, and spectators would soon suggest the company should buy back Viacom Inc. to reestablish its scale. And now, Netflix—a DVD-rental-turned-online-streaming service—has unseated the final holdout, Walt Disney Co.