Be aware due to the ajax api technically proficient users can still add products over the api when they are published on the online-sales channel requiring backend solutions if this is a non-starter.
So make sure inventory control is turned on with 0 inventory.
If that's unnacceptable you basically need to make pages with that product information and either send customers to /pages, possibly use redirects, or do advanced theme customizations to pull the relevant page-information into the matching /product urls keeping in mind if a product is unpublished then it's /product url endpoint returns a 404 impacting SEO.
Band aid fixes:
Depending on theme there are pre-existing posts on hiding add-to-cart buttons with CSS.
But note depending on your terms, and demand for product it's simple for users to unhide the product.
For OS2.0 themes make an alternate template for those products with the product forms buttons settings disabled.
https://help.shopify.com/en/manual/online-store/themes/os20/theme-structure/templates#create-a-new-t...
For vintage themes, In some situations this can be like a back-in stock notification customization:
https://community.shopify.com/c/shopify-design/forms-add-a-back-in-stock-notification-form/td-p/6165...
If you need this setup, a consult, or a more advanced customization you can contact me using info in my forum signature. Please provide context: store url, storefront pass if applicable, example product url, theme name, and issue.
