A greater percentage of reddit is younger than some of them realise. So many redditors are going to be used to new reddit, and plug-and-play services in general. Kbin and Lemmy look like old.reddit, and they require them to understand the concept of what a 'server' is to even get started. This is knowledge they've never needed before to use the services they want to use.
Imagine spending all your life eating McDonald's and then somebody told you homemade burgers are way better quality, taste better, cheaper, etc; then when you ask how to get a taste of those bad boys they start with informing you that you'd need to grill them. It's not hard, it's just new.
they require them to understand the concept of what a 'server' is to even get started.
I've known 5 year olds start minecraft servers. And understand that each "world" is an "instance". But that's aside the point, as you're right that even Help-Desk IT people struggle to understand the difference between computer and server.
It's not hard, it's just new.
The "new" part is what gets people. All of this is new. Even the implementation of all of this "fediverse" is new. It will come with time! People probably didn't understand email vs snailmail, and probably had an even harder time with SMS/IM vs email when all of that came about just over 20-30 years ago. Most of these "complications" are from people that grew up knowing that the "internet" is basically 5 or 6 social media sites for very specific uses, and those 5 or 6 sites are older than most of the people using them, so that's all they know. Even for a dude in IT, the fediverse was a new concept to understand, and even difficult to understand how it could best be implemented for the masses.