It's interesting to note that these are not natural forests, but essentially man-made tree plantations, reforested since the 18th century after the natural forests had been eliminated in the centuries before mainly because of ore mining. Same story further to the south-east in the Ore Mountains.
Getting rid of the spruce tree mono culture and letting a mixed forest regrow will be a good thing even if it will take a century or more (that's at least what the strategy seems to be in Ore Mountains).
This seems remarkable from someone who grew up in Toronto, where chunks of ancient forests (since the ice sheet retreated ~12kya ) are scattered everywhere.
The Swiss National Park was mostly untouched since 1914: https://en.wikipedia.org/wiki/Swiss_National_Park However, that probably does not qualify as old growth. The list you linked to does not list any forest in Switzerland.
Apparently parts of Ruegen island are "old forest" and some patches here in there in nature reserves, but I guess one could argue that even the old Slavic and Germanic tribes already "cultivated" their forests.
Getting rid of the spruce tree mono culture and letting a mixed forest regrow will be a good thing even if it will take a century or more (that's at least what the strategy seems to be in Ore Mountains).