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.
I'm sorry, you might not mean that literally but too many people perpetuate the myth the taxes and or social security contributions eat up all wage increases or that people get even less due to higher taxes.
That is complete nonsense. The total tax and social security contribution would have to be at 100% for that to be true.
If you want people to be able to afford more with their money, then I'd advocate for lower VAT and/or dropping the VAT for basic foods and products to 0%. That wold also help the poor more, serve as a better social redistribution measure and could contribute to more domestic demand.
If we are not talking about taxes but social security then I agree that there need to be significant reforms.
I agree that IF you have to spend money on defense, you might as well do it domestically but that should be an added bonus, not a major point.
Economically speaking, the defense industry is a terrible investment. At best the goods it produces just sit there and are never needed, at worst they are used up. The US military industrial complex is not a healthy, useful or productive industry. Jobs in just about any other industry are more useful for society and/or the economy.
Defense spending should be purely driven by security requirements. Potential jobs created are a nice bonus but should not be part of why you're doing it.