Useless to whom
"All art is quite useless", Oscar Wilde wrote in the preface of his 1890 philosophical novel, The Picture of Dorian Gray.
And that can be true not just for art, but almost every other thing in the world. I'm yet to see a piece of art considered to be both 'useful' to and loved by everyone.
Art, in this sense, ranges from a creative project to a technical project, a social experiment, or even code.
Decide who it will be useful for. It's okay if it's useful only to you. If that's the case, you can sieve the feedback you get from others through that lens.
After all, we gain meaning from art based on the meaning we decide to give to it.
Your art may likely be useless to the majority. It's not for them. Focus only on those it is useful for.
The excuse for making a 'useless thing' is that you admire it so much to the point of creating it. Even if it is useless to others.
If it passes the learn test, you can build art for art's sake.