Your personal experience does not define the platform. Yes, the fediverse got an influx of new users right after the Reddit API change. So you observed the similarities and concluded that this was designed as a replacement. That is just not the case. It got your attention because of that incident, but it had been its own thing for a quite a while already. The design is merely a sensible approach to the framework. You will find the same on many other social platforms because it’s a good design. Also, all these things are just front-ends to databases and often the designer will tailor that based on what they know is already popular.

But for Lemmy there are numerous front-end apps already that are not all the same. They’re designed slightly different from one-another, but mostly follow the same basic structure because - once again - it works well for the platform.

I’m not disagreeing with you that there’s a lot of similarity, I’m just saying there’s nothing about Lemmy that is intended as a reddit replacement. It merely serves that purpose fairly well. But there’s a lot of difference too, because it is not a replacement by intent.