Hi Davidihewlett,
An alternative is to go to the Home Screen by saying "Go home". That way, you won't need to go through the other commands for quitting out of an app.
Check out that suggestion here: Use Voice Control to interact with iPhone - Apple Support
Learn Voice Control commands
When Voice Control is turned on, you can say commands such as the following:
• “Open Control Center”
• “Go home”
• “Tap item name”
• “Open app name”
• “Take screenshot”
• “Turn up volume”
To learn more Voice Control commands, say “Show me what to say” or “Show commands.”
Typically, there's no reason to quit out of an app, unless it's not responding. You can see that outlined here: Quit and reopen an app on iPhone - Apple Support
If an app isn’t responding, you can quit it and then reopen it to try and resolve the issue. (Typically, there’s no reason to quit an app; quitting it doesn’t save battery power, for example.)
If you would like to leave feedback for Apple on any suggestions you may have with Voice Control, then please use the following link where your voice will be heard by the appropriate teams: Product Feedback - Apple
Kind regards.