I wanted to try the fediverse for a long time but always found it too complex/confusing and with the whole reddit situation I finally took the opportunity of actually giving it a try and personally, Im enjoying the change. Lemmy is small but it will grow, but I keep seeing ppl complaining about the learning curve and that is too complicated. In my opinion want the main "issue" is the freedom of CHOICE. We have been used to having limited choice and with the fediverse there is so much of it, choice in instances but also in services since, since from what I understood, ActivityPub allows you to see Lemmy from a mastodon client and viceversa.
From the instances, the learning curve is when signing up, when joining communities and overall browsing. People got used to centralized services so when you recommend Lemmy they expect a single website. But the reality of Lemmy is that being on fediverse its decentralized with multiple instances to choose from. However, on reddit (or other platforms) every account is technically equal but since instance can choose to limit stuff like downvote or creation of communities, depending on where you create your account you might get a different feature set.
Then comes the fact if communities you want to join are in a different instance you need to account for that with the @instance-name. This also means that if you are used to only browse while not being logged-in, on reddit is simple since its reddit.com/r/subredditname, on Lemmy this becomes lemmy-instance.tld/c/comunity-name@community-instance , which adds a layer of complexity. Eventually people will learn where their communities reside, but for now is yet another thing one needs to know.
Also another major thing is that in reddit each sub was unique. Here multiple times I found the same community on different instances. Which is good for the whole decentralized aspect but can be very confusing when trying to join.
I'm new at the federation but one thing that would be cool to see is that communities over different instances were the same. For example, if tech@instance1 and tech@instance2 were the same community, there would be less confusion when trying to join since the "space" was the same. I think it would improve reachability (local feed) and so that if one goes down the community is still there, but mainly understandability since one would not need to figure out which is the community that you actually wanted to join.
Finally, I want to thank all the developers and and creators that allow such place to exist and continuously try to make it better.