To me the test of how useful or uselessness of a particular thing is completely dependent on how and how much its end users interact with it.
To me it does not matter how long you have toiled in writing the code or the choice of color pallets or whatever.
Does the end user use it?
end of story.
They should either love it or hate it but never ignore it.
If they love it and use it.. Don't repair it if it ain't broke.
If they hate it but still use it,I see it as scope for improvement.
But God forbid, if they just do not care / know about it, you as the creator are in trouble.