As others have said, you don't know.
But start with you: Are you building it because you want to build it, or because you want it? Are you in love with it as a project, or as a product? Is it something you want to use?
Then, when you have it as a just-barely-usable thing, give it to a few people who have the same need. Get their feedback. Does it actually help them? If so, then you may have something.
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