As for usability, I'd honestly like to know better in what ways did you think the usability was terrible. Just saying the usability was terrible is kind of an abstract statement. Thanks for the feedback though, no matter how harsh, always appreciate some feedback :)
Please read the site guidelines too: https://news.ycombinator.com/newsguidelines.html. Note this one: "Be kind." Note also the guideline against calling names. Don't call names about people's work ("ugliest I've ever seen")—rather, show them specifically what needs improvement and how they might make some improvements. You can and should do that without insults.
Anyone sharing their work is making themselves vulnerable. Keep in mind that however aggressive or unpleasant you think you're being you're almost certainly underestimating it (we all do). It's going to land with readers as 10x more so, and probably 100x more so with the person whose work you're attacking. I'm sure you didn't intend to be mean, but on the internet, it's necessary to disambiguate one's intent: https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so...
Keep in mind also that it's extremely easy for internet forums to degenerate when people post like you did here, because people who don't want to be part of a poisonous culture gradually withdraw, leaving a community of mostly-jerks with nothing interesting to talk about.
Fortunately, there are ways to share all the same relevant information without putdowns. Please do it that way instead, so we can keep HN from becoming a nasty place.