Dont know if this will help, but my youngest has an iphone x and I can block an individual app
in settings go to screentime
app limits
add limit
click the arrow to the right of games
select the game
click next
select the time limit, you can select 1 minute, block at end of limit
you can get pretty specific about what can be used and when
or you can just delete the app and set the phone so apps cannot be installed without the parent passcode.