If you prefer the UI of one to another now you have to create a brand new community which is going to take time to fill. I use old.lemmy.world because I like the old reddit UI
I think there's a misunderstanding?
You can use remote communities, for example: [email protected] for you is https://old.lemmy.world/c/[email protected]
the "Old" UI seems to hide the list of communities, but it's here: https://old.lemmy.world/communities