I don't have skin in this game and will probably never use it anyways, but to me that is a non starter for this whole project. Why would I want to limit how often my friends can post? The problem with FB isn't that my friends post to much, it's that I never see what my friends post.
This argument makes sense to me in a public space, like twitter. But among a close knit group of friends? Not one bit. They are directly advertising this as a space built for "friends", not influencers. Having to time-filter your friends sounds like a really negative friendship dynamic.
Then you can already use a Telegram channel. (Or an RSS feed if your friends can bother.) It fits your needs pretty well. You don’t need a new social media app.