All Facebook pages are being switched over to the New Pages Experience, but we don’t know when that will happen for each page. It’s a slow roll-out process that began in 2021 and is still ongoing.

Here’s more info directly from Facebook:
https://about.fb.com/news/2021/01/introducing-the-new-page-experience/

There’s also info specific to the New Pages here: https://www.facebook.com/business/help/NewPageExperience/

Requesting to Switch Page on Facebook

You’ve heard all about the change, and you’re seeing New Pages Experience pages all around Facebook, but maybe your page still hasn’t changed yet.

Don’t worry, I understand! Only 40% of our pages we manage have changed to New Pages. I don’t know when the others will change, but it WILL happen… sooner or later.

Unfortunately, you can not request to switch to the New Page Experience in advance of getting the notification from Facebook.

Once again: You can NOT request the change to a New Page, but you will be notified by Facebook before the change takes place. Be sure to watch your email and on-page notifications in Facebook for that.

Please accept this change when notified by Facebook.