Why is there new UI?

I don't like this new UI, I thought this was in beta.

It was ... then they decided to move it to Production.

New features are getting tested by beta members, then it will be officially released for everyone.

Beta testers need to increase the range of their testing. Too many bugs making it through to Production.

Me too . The new ui is weird and unrealistic . It needs to be changed back into the original one

You don't need to bold everything. 

Ever heard of law no 6 of 48 laws of power ? "COURT ATTENTION AT ALL COST"

Btw i don't intend to be rude . I apologize if I've responded wrongly .

It had been working fine for months (dislike of the format isn't incorrect operation). Some updates were made based on feedback. Additional updates were made after additional feedback when the update started rolling out more widely.

When will it be site-wide?

It actually is as of today

Ever heard of Rule #4 of how not to advertise/spam? "Don't make yourself look more important than everyone else."

google's response:
"...citing Robert Greene’s 48 Laws of Power to "court attention at all cost"—is generally considered antisocial in a collaborative community space..."

Anyways, why can't play be customized for the sidebar? Why not let it be like the rest? I'm kind of trying to like, move every "general tab" to More or Other or whatever it was, and having the stuff I actually use on the side, but play just is unable to be moved?

I'm not a fan. But they will not be changing it back to the other one, so better get used to it 😁