OP what we need is like a reverse DoorDash app for restaurants like yours.
Guest makes a reservation, gr8.
But in order to keep it, they need to log on to the app and confirm their intention to use said reservation 30 minutes before, and at that point the app puts a small hold on their card.
App tracks GPS on primary guest, and if they are not en route to your restaurant it alerts you so you can have staff call them.... maybe they're running late, maybe the app is malfunctioning, etc.
If they do not show, they incur a monetary penalty, and you can rate them as a guest, so someone constantly telling you to **** off, maybe you just don't allow them to make reservations any longer.
For good guests that you've previously known to be reliable, you could offer them perks thru the app at your own discretion.... discounts, free drinks, free appetizer, free desert.... and combine it with your changing menu to push certain money maker dishes out of your kitchen.... first one is free, then they order it every time.
I wouldn't personally be offended by what the OP proposes, but I don't know that it would efficiently solve the problem.