It lacks the critical mass of users needed to make even moderately niche communities feasible; basic examples are: City communities, State communities, communities based on car make/model - these are types of communities that Reddits excels at having and it's because of the size of the user base. The only point I'm making with this is that Lemmy is a very long way off from being a viable replacement for Reddit.

Next big problem is: Lemmy has a HORRIBLE new user experience...which I'm sure is significantly responsible for slowing Lemmy adoption. Single biggest issue is content discovery (which is just-ok if you got lucky and joined a super-massive Lemmy instance when you first joined, all the way to an atrocity if you got unlucky and joined a small instance when you first joined.

There's also a lot of complicated activities needed just to be a functional Lemmy user: like regularly backing up your user/instance preferences (including subscriptions) and replicating those preferences into another account/instance in case something happens to your current account/instance or your instance becomes temporarily or permanently inaccessible. This is asking too much of your common non-technical user, but it's still currently necessary just because of how often instances have problems. Think about all the user accounts on all the .ml instances that had to be re-created from scratch because there's no built-in way for users to do it. Users should be able to sync their user accounts similarly to how instances sync their content with each other.

For the record, the first instance I created an account on (when I was a brand new Lemmy user months ago) was a very small instance (but recommended on the very first page of the official join-lemmy.org site), and there just wasn't functional content discovery at all on that instance. It was a barren wasteland. The fact that servers aren't even aware of what content is out there on federated systems until some user on that system already happens to know about the content/community and subscribe to it is setting a lot of new users up for failure. Once I realized that it sucks being on a small instances, the second account I created was on Lemmy.world, but that instance suffers from it's popularity and is the frequent target of DDOS and was going down for me several hours a day. So, there's also a penalty for joining a big instance. I ultimately had to create numerous accounts on numerous instances and then try to keep the user preferences in sync across multiple accounts on multiple instances so that I can easily swap to a different account when an instance had problems.

Elitist user base: I swear, some lemmy users are worse than the old BSD forums and worse than stack exchange when it comes to taking criticism about the platform. Guaranteed, this comment will get downvoted, and I'll be mansplained about how content discovery is facilitated through having to have foreknowledge about some 3rd party websites that keep track of communities (which don't always work because not all instances can be indexed yet do to a laundry list of other problems), and what an idiot I am for not knowing this, etc, etc.

Having to go to this length just to use a reddit alternative - that's unacceptable to most non-technical users. Lemmy doesn't stand a chance of gaining momentum until these issues are solved.