It is for all intent and purpose cleaned up, finding eod is usually things people collected and shouldn't have or things deeply buried. Korea, Vietnam, Cambodia have active surface level minefields that have been known and documented since during the war, it isn't a matter of hard to find in those places it's a matter of allied powers simply not having any interest in demining the places they mined.

Things in the area of the alsace go up and rarely come down it's an incredibly mountainous area, there are still functional artillery pieces out there. That is however much much different than knowing you put mines there, knowing civilians cross through it and yet refuse to clean it up. And to add to your point there is an area of France that quarantined since ww1 because of the level of arsenic, but again that's an exception not the rule.