Why can't I rename a Pages document on my MacBook?

Are you renaming the document from its window title bar? There is an usability issue here that dates back to the pre-OSX days to NeXTstep (well over a quarter century and continuing).

When you rename a document YOU ABSOLUTELEY MUST tab out of the field to remove its keyboard focus. If you just hit Enter the name reverts to what it was before.

This is a remnant from the NeXTstep times where each and every textfield showed this behavior. It got fixed sometime early in the lifecycle of OSX but sneaked back in when that "Edit on Window Title Bar" was introduced. As far as I know this is the only place in macOS exhibiting this behavior.

Call it a bug, a usability issue, a feature, a nod to the past if you want, but it is annoying and even though I know about this it happens to me, too, that I hit the enter key instead of first tabbing out of the field.

Assuming the Pages document to be renamed is not presently open in Pages, one applies a right-click/control-click/two-finger tap of the document name in question and from the secondary Finder menu, chooses Rename. This will automatically highlight the basename of the document where one can simply type in the replacement name. Then press return to set the name and click elsewhere to deselect the document. No tab is involved.

I just performed what I typed above and it works exactly as it has for the last several years.

By the way, all capitals is considered "shouting" and shouldn't be used.

Tested: Pages v14.3 document, macOS Sequoia v15.3.2.

Tab key doesn't work on my side.