Mr. Robot's Season 3 finale probably could have sufficed as a series-ender if the show wasn't granted another season, but oh-so-much would have still been left on the table. "shutdown -r" certainly followed many of the rules of an endgame (for a Trilogy, since this was the 3rd season) given all the "back to the start" twists it brought into play - secret family members, false memories, etc - but it also worked as the jumping off point for a fourth season adventure that could/should embrace the sci-fi the show's been teasing. As Irving said, holding Gore Vidal's "Death Likes It Hot," you gotta have a "wow!" ending.