Lemmy is not ready for primetime yet. There is no way that 400 million reddit users can move here, when the biggest servers struggle with tens of thousands, and the total users active on Lemmy in the last month is around 30,000 (up from 1,000 a couple of weeks ago).
Not to mention that Lemmy is really not general-population-ready. Explaining it is a bit of a mouthful, but manageable. What's not manageable for most users is things like:
- Most people have no idea how to start. The join-lemmy site just points you at a massive list of instances and hopes you know what you're doing
- if you're reading a post on another instance and someone links to a community, the link won't work and you'll have to copy/paste the URL into your own instance.
- Hot/Active don't work because of a bug in refreshing them
- The post you're reading can suddenly change, especially if you have two tabs open with different posts
- If you want to subscribe to a community but no one on your instance has searched for it before, the search will show "No results" - but then suddenly have results if you wait 10 seconds (or sometimes never show it until you refresh)
- Posts just appear at the top of the list, and worse, pop up as a notification. Great when there were only 1000 users but now the All page just gets notification after notification and the feed keeps moving
- The right combination of events means that a community can just disappear
- The search form doesn't let you change between Subscribed/Local/All unless you search for something first
- Moderation is still a problem. One of the big instances is wholesale blocking dozens of instances, including some big ones, because they can't handle the moderation. When it comes to moderation, I suspect most of the big instances are just...not.
This is just off the top of my head. Lemmy is great because we are building a new community, but the polish will come with time. We need to slowly and organically grow the community (lemmy.nz as well as the "Lemmyverse"), so issues can be worked out. Luckily places like this tend to attract a more technical audience as they are more willing to put up with bugs, and because Lemmy is open source many of these people can help write code for bug fixes and new features. The number of people helping has gone up significantly in just the last two weeks.
So what I'm getting at is if people are unhappy with the actions of the reddit board, they are (probably) welcome here. But we do not need a significant number of new users overnight - that's only going to end in disappointment for everyone involved.