Changing the default and its formatting does not remove any controls from that card. The hours/minutes controls you see are a result of the SP list's column allowing date & time instead of date only. You will need to remove those controls and ensure the Update property sends your formatted date back to the SP list. You may want to change your SP list column to reference dates only; otherwise, it will show a 12:00 defaulted time in the list.
Also, your formatting statement should probably read: Text(ThisItem.DateJoined,"mm/dd/yyyy")
Hope that helps,
On Update Property of the DateDataCard, change it to:
I have tried below one, but still it is not reflecting. Please help
Did you make any changes to the controls, the SP List column, or implement any of @eka24 's suggestion? Please share any new output/errors from your app so we know what's going on.