You can disable contact us page in Magento 2 using configuration settings.
By default, the Contact page is enabled and you can check the contact us page using URL, <SITE_URL>/contact
If you want to modify or change contact us page with your custom contact page, you can disable the Contact page using the below settings.
Contact Us Page Scope is Store Level, You can Enable contact us page at one store and disable on other store based on your settings.
Setting to Disable Contact Us Page,
Go To Admin Panel,
Stores -> Configuration
Now Click on General Tab,
General -> Contacts -> Contacts Us
Set No to Enable Contact Us Dropdown field.
Clear Cache and check the URL again.
When you refer to contact us page, Its display 404 page not found.