It's a matter of degrees. The 2013 draft was really odd in that the best player was taken 15th and the second best player was taken 27th, but there were a number of decent players (Adams, Oladipo, McCollum, Porter, KCP, Schroder, even Olynyk) and they took a guy who literally wasn't even an NBA player. Darko played for 10 years and was a decent rotation player for a good chunk of that. The book isn't yet written on Fultz but barring something new he'll stick around for awhile longer.
Slightly off topic, but while Fultz and Darko were certainly busts considering who came after, I'm not sure anyone can beat Oden in that regard. Not just because of who came after him (Durant is likely going to have a better career than anyone drafted after either Fultz or Darko), but because unlike Fultz/Darko (and Bennett), Oden was seen as a generational talent. He was supposed to be a cross between Mutombo and Ewing, and he ended up playing barely 100 career games over 7 years. Maybe he gets a pass because of injuries, but considering expectations, alternatives and results, I don't think anyone is as perfect a bust as Oden.