The main problem with unions in Germany is that they block companies from adapting to changes in the environment quickly. Companies become heavy behemoths and end up suffering from it, which ends up damaging their own employees as well.
Larger companies move slower, larger companies also tend to have a stronger union presence than SMBs
I like the concept of the union, but I think that IG Metall is not the good implementation of that. At least not for white collar workers.