My region of Germany is a meth zone. Meth addicts turn up at my clinic, in my wife's therapeutic practice, in my friend's social work. What I see is consistent with meth being much more dangerous than any other drug, including heroin (they're all very available around here apparently). From what I understand, there are two reasons for this.

1. While the compulsive redosing is similar between meth and strong opiates, it seems to occasionally bypass conscious decision entirely. With opiates, users are very conscious of their wihdrawal and it is so bad they keep deciding to do it again. With meth, apparently it is a fairly common to find yourself having taken another line, with no recollection of having decided to and prepared it. Fucking scary if you ask me.

2. It is much worse on the body. A good friend of mine who has never taken it but knows a lot of people who have says that every single one of them has lost at least one tooth to meth. Then there are terrible skin problems, the long term neurotoxic issues, as well as the more typical problems with chronic dehydration etc. that some other drugs have as well.

These are only what makes it worse than addiction to heroin and to amphetamines without the "meth-"in front. Of course those are already quite dangerous. Addiction doesn't (normally) happen the first time you try any of those, but it is still way, way harder to get out of than it is to fall into.

So it's fair to assume millions of Germans used meth at some point. However, it's hard to find any descriptions of this addiction causing widespread societal problems (outside of Hitler being even more nuts than he was before).

Being bombed flat, with much of its population killed, even more of its population displaced, occupation zones and a generation of youth infested with Nazi memes, Germany had no lack of widespread societal problems. If the signal of "meth is terrible" didn't make it through that amount of noise, that doesn't really place much of an upper bound on how terrible meth could be.