Convincing yourself that future success isn't predictable is actually pretty easy. Regardless of how technically awesome someone is, there's a random variable that can dramatically affect one's future success: the candidate's co-workers.
Anyone with a few months experience at a big company knows that a new hire's coworkers are, for the most part, selected randomly. When the co-workers match, everything can work out, even if the candidate isn't technically strong. If the co-workers don't match, for whatever reason, the working relationship can easily fall apart.
I don't know what the ultimate solution is. Even work trials aren't perfect since company and team structure change. Accepting the unpredictability of future co-worker relationships makes it easy to see there's no magical solution. Understanding this might help things move in the right direction.
Anyone with a few months experience at a big company knows that a new hire's coworkers are, for the most part, selected randomly. When the co-workers match, everything can work out, even if the candidate isn't technically strong. If the co-workers don't match, for whatever reason, the working relationship can easily fall apart.
I don't know what the ultimate solution is. Even work trials aren't perfect since company and team structure change. Accepting the unpredictability of future co-worker relationships makes it easy to see there's no magical solution. Understanding this might help things move in the right direction.