Of sport in general?
There's all kinds of aspects to it beyond just winning, fitness, entertainment, money. Success of failure can be different from person to person on this, there's not really any objective right or wrong.
Would you call every person that took part in the London marathon but didn't finish first a failure?
If you're following Spurs and are going to get to the end of your life and consider it a failure or a waste of time if we haven't conquered all and forced the other sides in the world to give up because we're so good then you're going to end up disappointed.
All football is is a never ending sequence of occasional successes, some small like winning the match on a weekend, some big like winning a cup, and some massive like winning a League or the CL, and on the flip side there's always a failure around the corner, losing the next match, knocked out of a Cup, etc.
There's no definitive success/failure really, because there's always a next season.
I've lost track of where I'm going with this now tbh.