You can turn off comments by default on all new posts…

From WordPress choose settings > Discussion >  and then  by unchecking “Allow people to submit comments on new posts”)

You can turn them back on an individual post if you ever feel the need to

• Edit the post or page in question
• Choose screen options (top right) and make sure the “Discussion” box is ticked
• Scroll down right toward the  bottom and you’ll see a panel for Discussion and an un-ticked “Allow Comments” box
• Tick that and then comments will be allowed for that page/Post only