Most people who have the need this product is meeting will have already encountered Calendly as it is ubiquitous in the space. It's basically a generic term like "Zoom" at this point. "I'll send you my Calendly link" is something people will understand to mean send you a meeting scheduling link.
So "An open source Calendly alternative" is quite clear for most people who want to make use of this.
Their messaging is focused on reaching people who might use it, not the people who won't. As you note, after going through the site, the product is not something relevant to you.