I'm sure you didn't mean to, but this comes across as a shallow dismissal, which is against the site guidelines (https://news.ycombinator.com/newsguidelines.html): "Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something.", as well as the Show HN guidelines (https://news.ycombinator.com/showhn.html).

A comment like this could turn from a bad one to a good one if it were written more in the key of curiosity: what are the similarities or differences? what are some pointers for further development? and so on. If you know more than someone else does, that's great, but then please share some of what you know so we can all learn.

Telling somebody that their project which they've been pouring their passion and creativity into is merely reinventing some well-known thing that's been around for years is going to come across as a putdown even when it isn't intended that way. The effect is to shut down creativity and exploration, which is the opposite of what this place is supposed to be for.