I get utterly bored with new sports within 3-6 months. This has happened with every sport I have tried, no matter how much I loved it at the beginning.
Some people enjoy repetition. Some... really don't.
For me the challenge is to keep finding new interesting sports.
I've been boxing almost every day for almost 6 years now. The more into it I get, the more there is to discover and the tougher my sparring partners get. It really doesn't feel like repetition at all.
So maybe you just haven't found a sport you liked yet. Or haven't given them enough time to reach a level of mastery where it doesn't feel so repetitive anymore.
Some people enjoy repetition. Some... really don't.
For me the challenge is to keep finding new interesting sports.