From your comment "it's not good enough for me" tells me that there most be some way of refining the idea so that it does become good enough for you.

As a first step, talk to people who use your competitor's product and see if it is "not good enough" for them as well. Then ask them if your refining idea would make it good enough for them. After you've talked to enough people you will have a more clear understanding of what needs/problems/frustrations your competitor is addressing and what needs/problems/frustrations your competitor is not addressing.

Then you can start implementing the solution for those needs.