In Salesforce, if we try to save the changes made to one profile, we face an error similar to the one shared below, where the related objects are listed and the user doesn't possess access to those objects.

To resolve this, you need a Salesforce interface that would let you grant permission to all the objects in one go. Hence, to enable that, you need to disable the "Enhanced Profile User Interface" for your org. 

When this feature is enabled for any org, the profile page looks like this:

Here are the steps to do so:
1. Go to Setup -> Type "User Interface" in the quick search box
2. Uncheck "Enable Enhanced Profile User Interface" and save the changes.

After the changes, it would look like this:

Once these changes are saved, you would be able to edit the profile permissions and enable it for all the objects in one go.