The usefulness question is the a poison to discovery.

How many things we use in our daily life would have survived the first peer review for usefulness?

The printing press? Makes no sense, use scribes. The public cant even read.

The internet? Why would people use a computer to communicate and share data? Its super slow, just send a magnetic drive or even better, copy the images on paper.

Solar power? We have coal, oil, nuclear, that stuff has no future.

If something is not useful, in dubio assume, that it is, but you just are not capable of seeing the use or the market it will create.