Think about things from the point of view of someone who has never used Reddit or the fediverse, but you've heard about them both from recent news articles and want to see what they are about.
Reddit:- You Google Reddit and your first result is Reddit.com. You click the link and are presented with the front page. You from scroll from a few hours and end up signing up and staying.
Lemmy:- You Google Lemmy and your first result is a wiki article for Lemmy Kilmister... Your second result might be join-lemmy.org, which you're smart enough to realise it's probably more likely what the news is about.
You click join-lemmy.org and are presented with a page of information about the fediverse, links to set up a server and pictures of code...
There is very little chance you're going to investigate further.
If we want the fediverse to replace Reddit then either
A) Lemmy needs to improve its initial impression and Search engine optimization
B) We should be promoting a different platform with a better initial first impression.
I'd recommend kbin personally as it gives the same sort of experience as Reddit from the initial interaction.
I tried Lemmy yesterday but today, probably thanks to the influx of new users, it's been extremely slow to the point of unusability. So now I'm trying out kbin which seems to be running faster (although still slower than old.reddit). Ignoring those issues, I can't decide yet which I like more.
I'm also still kinda confused about all the Federation stuff. So supposedly you should be able to interact with kbin hosted stuff on lemmy and vice versa and I can indeed see posts from lemmy on kbin's "front page" but what if I happen to come across something directly on the lemmy.world website (or any other Fediverse instance for that matter, where I don't even have an account), is there an easy way to access it from kbin.social?
I feel like the decentralized nature of Fediverse is at the same time its strength but at the same time makes it harder for users to switch.