Why does wordpress visual page editor slow down?

Question

WordPress

There was a problem with the visual page editor in wordpress - when you try to edit, create, publish a new or old page, wordpress starts to slow down terribly and comes off after 10 minutes.

I emphasize that the problem is only with editing and creating pages. If you open the record editor, then there are no problems.

The rest of the wordpress sections work as expected - without brakes. From this we can conclude that there are enough resources.
What was the problem after?
The problem appeared after it was loaded through the WP All Import plugin - more than 25,000 pages
Actions that were taken:
- completely disabling all plugins
- disabling additional elements in the wordpress page editor (Screen Settings → Page Attributes, Page Images, Custom Fields, Discussions, Label, Author)
None of the actions taken helped to correct the situation.
Please tell me how to solve this problem.

Answer 1

You need to remove the "Page Attributes" block
Here is the code:
function remove_page_meta_boxes() {
remove_meta_box( 'pageparentdiv', 'page', 'side' );
}
add_action( 'add_meta_boxes', 'remove_page_meta_boxes' );