The library is in the "More" tab. I personally think the change looks better. 4pc and Daily are easily accessible and didn't really need a tab in the play menu.
Not a Bug [✓]: Missing PLAY menu choices - have been moved

The library is in the "More" tab. I personally think the change looks better. 4pc and Daily are easily accessible and didn't really need a tab in the play menu.
Again, this is a personal opinion.

Picture says it all, mostly:
Where's Library?
I liked the + New Game choice
etc.
etc.
============================
This kind of slip up is totally avoidable and should never see the light of day even in Beta! A simple QA, quality assurance, check of comparing the old menus to the new and ensuring no dropped entries is a 15 minute effort.
Chess.com you can do better!
If you want the old one, then leave beta.
It will update to the old one

The menu has been in staff testing for a while as I understand it. They were also trying to streamline things

This isn't a slip-up, it's an enhancement and you just need to get used to the change. They probably ran some analytics and saw most people don't use that new game button and removed it.

I stand corrected. Where things went was not immediately obvious
The + New Game is gone, Clicking Play is equivalent.
Daily Chess is accessed via Play
4-Player Chess is access via Variants
Library is hidden under the ... More Features.
The ... menu is a bit overloaded

I will miss the 4 player Chess.
4-Player chess is variants
Library is more
Daily games is on play

This isn't a slip-up, it's an enhancement and you just need to get used to the change. They probably ran some analytics and saw most people don't use that new game button and removed it.
It's extremely valuable to players like me, I record all of my opening theory there.
They didn't get rid of it. They just moved it. The same amount of clicks lol
Picture says it all, mostly:
Where's Library?
I liked the + New Game choice
etc.
etc.
============================
This kind of slip up is totally avoidable and should never see the light of day even in Beta! A simple QA, quality assurance, check of comparing the old menus to the new and ensuring no dropped entries is a 15 minute effort.
Chess.com you can do better!