Lifting the minimum wage directly impacts the available income of the lowest income classes, who in turn spend most of their income on consumption, increasing domestic demand and thus also helping the economy.

…except when it doesn’t, because the ever-increasing contributions to the Rentenversicherung and Krankenversicherung just eat up all of the brutto increases, leaving people with effectively the same netto. Same applies for every wage increase for every other income class.

Your points are valid, however please note I never advocated for just reducing the income tax alone, but rather the Abgabenlast that all workers have to carry. Primarily health insurance and pension insurance. These systems have become unsustainable (though I would argue they never really were, the issues were masked by a different age pyramid back in the day) and will have to be completely overhauled, the question is: will someone take the plunge and do this before everything collapses?