I agree that Roblox needs to take action on this issue. Nothing is really changing, they just wanted to add an extra layer of security to prevent people from hacking in an inappropriate thumbnail without moderation. You literally just have to press a button and it'll be checked for free.
I do agree with some of the concerns here though, automation for older games needs to be addressed, as this move was a bit hasty and could have been done better.
Here's the best course of action I see for moderation:
When a user visits the page of a place that hasn't had its thumbnail updated..
- Generate a hash string of the places rendered thumbnail.
- If it produces a hash that hasn't been penned before...
- Render the game thumbnail and icon, and push it into the moderation queue
- Put priority on pending thumbnails for games that are actually being played
- Otherwise if an thumbnail has been generated already
- Recycle the game thumbnail and apply it.
This should resolve most of the active cases pretty quickly.