Pull not being a good model of two way communications is going to be the major blocker here in my opinion. It's going to mean that people are only going to see comments and reactions on their posts or comments from people they already subscribe to, because their RSS reader would have no possible way of knowing if anyone outside of that list commented, since you can't get notified of content sources you don't already know about, only poll ones you already know. That's already bad enough (one of the big negative things people with large followings on the fediverse talk about is how they can't see what people are saying in the replies to their posts a lot of the time if the servers those people are on are blocked by their server, which means hate and harassment and one sided conversations can fester, and often many commenters can't even see each others' comments, leading to people saying the same things over and over exhaustingly). This also means that people who don't have any followers will literally be essentially muted by default: no one will see their comments or interactions, because no one polls their feed yet, which means that it's basically pointless for them to interact at all, which sounds dispiriting and would probably lead to no one wanting to use this type of social media — moreover, it also creates a catch-22 problem, because a major way to get followers in the first place is to directly interact with other people and bigger blog posts, to make people aware of you and maybe get some of them interested in hearing more of what you have to say, yet in this model, you can't really interact until you have a following already, so your main means of getting a following is gated behind needing a following to work!