The fact that it's private and on-device doesn't change the fundamental issue with it. It doesn't provide more relevant results than subscribing to communities you are interested in. All it does is create toxic echo chambers because you will get served the same type of content that is getting the most engagement over and over again.

It's the warped perception of people fleeing to Fediverse, not because it's Fediverse but because it's not Twitter or Reddit or another platform that got enshittified, and they just want to re-create the same toxic status quo they used to love.

All that said, I will always encourage open source development and good luck with your project.