Maybe they should just forbid or discourage tourists from countries that cause the most problems, such as Britain and the US. I'm sure Japanese tourists never litter there.
What they really need to do is come up with a "preferred tourist visa", where people (regardless of national origin) are only able to get this after being interviewed to make sure they're properly respectful of the local culture and environment, and if they get caught doing something wrong (like littering, going into off-limits areas or past safety barriers, etc.), get their good-tourist visa revoked. Interested countries like Iceland can then only allow people with this visa to travel there.
It would be similar. Any "vouching" system is kinda like this, and how useful the system is depends on how much you trust the entity that does the vouching.
If you don't like China's social credit system, what do you think of America's "TSA PreCheck" system? It doesn't bar people from traveling, but it does give special privileges to some.
I honestly don't see a problem if some countries decided to cooperate and implement their own "tourist blacklist" system to keep out tourists who have proven to cause problems: it's their right to refuse entry to any non-citizen they wish.