They basically try to centralize the platform.

No, they don't, I don't know why you think that, this is really what federation is all about, seamless communication between servers, all they do is make it so that linking to different posts across the fediverse doesn't log you out, or remove you from your instance unnecessarily

The other one ALLOWS you to categorize subreddits. Neither of these are bad things in any way, and if you don't like them, you can manually visit other instances, and simply not use the multireddits.

I like how Lemmy allows for sort of duplicate communities. Reddit already had that issue and people naturally flocked to the communities that had the content that suited them. I think it would behoove Lemmy to stay away from trying to centralize it all.

This won't change anything about that, it'll just sort them by category

Building a nice mobile android app Jerboa is pretty good but it needs some TLC. Timeouts happen frequently on my app and crash it/erase content I was reading

this isn't worth focusing on right now because: https://github.com/derivator/tafkars/tree/main/tafkars-lemmy

Provide better documentation/marketing materials for new users. I’m open to the idea of a centralized website where users can go to create accounts, learn about Lemmy, and maybe initially subscribe to popular communities

join-lemmy definitely needs an upgrade.