what your application offers is actually simple, namely offering an easy and secure way to share passwords, but in line with what other users have said, most people are more interested in using popular applications such as protonmail or whatsapp which use an encryption system and have trusted for a long time to send their sensitive texts.

moreover, the id system that you use is actually not very convincing for people because someone could guess a random id and log into someone's account (even if the attempt fails up to 3 times, this is still vulnerable) and this application is paid which for some people is quite annoying .

but even so, what you build needs to be appreciated. starting from the design, whitepaper, and faq, you explained it well. maybe if you improve the quality of the system there will be more people who trust to use your application.