Nobody in WWE's creative team wants any feud to fail.
How counter-productive would it be for WWE's writers to take two wrestlers, push them together in an on-screen rivalry specifically so it falls flat? Very. Everything WWE do is about making money, so whatever you see (whether it ends up working or not), they think it's a workable idea in the beginning.
That's not to say they don't have some stinkers from time-to-time. There have been feuds which, for whatever reason, have ended up outright killing a wrestler's career. Sometimes that's because the story was horrible from the get-go and totally unsalvageable, but other times it's down to a performer's own unhappiness with where their character is going.
Then, there are also those who will never fit in to WWE's way of doing things no matter how hard they try. Their feud sucks, plain and simple, and it's the reason they either never fulfilled their potential or left WWE entirely...