Based on your description I thought you meant only one page each, I'm sorry.
In this case indeed excluding by tag or category is the best option. The issue is that pages in WordPress does not have taxonomies by default, so no post tags, no categories. The input field below the page is to add extra tags to search for, but those are not the classic post tags.
To resolve that, I would suggest trying this plugin: https://wordpress.org/plugins-wp/add-category-to-pages/
This should allow adding categories or tags to pages. I would probably create a category, place the pages I want to exclude inside of it, then exclude that category. That should hopefully do the trick.
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