If you're in the camp that believes a championship is the only kind of success in sports that matters, then yes, the Sixers not winning a championship with any associated with The Process would make The Process a failure.
I am not in that camp, however. The Sixers amassed enough talent through The Process to be among the favorities, on paper, to win the championship in some recent seasons. That makes The Process a success to me. But winning a championship is hard and requires some breaks and luck and these Sixers haven't had enough things go their way to get there. Like, who knows what happens if Kawhi doesn't hit the 4-bouncer game winner against Philly to send them home in 2019?