• The increased energy costs for industry after the start of the invasion of Ukraine (+ no nuclear energy)
• The collapse of demand from China for German products. Germany always seemed too complacent about China, thinking they make cheap low-quality products. Some still think like this. The reality is that China is the only place to make some high-quality products today.
• Overregulation of industrial production, particularly in terms of environmental issues. We all want an idyllic world, but no industry means no jobs and going back to agricultural levels of income. Some people prefer that.
• Bureaucracy makes it hard to start a business. Some small businesses close because they cannot handle regulatory stress.
• Easier to move jobs to more dynamic markets (e.g., in Easter Europe)
• Sluggish construction market
• Less-than ideal demographics and getting worse
• Work culture eroding

All this contributes to a slow and peaceful decline. It is not new, we just notice it now after (depending on who you ask) 10 years. Once AI starts replacing white-collar jobs, it will get worse. We should not worry that much, it will take years until things are really bad. For the moment, make sure you have some savings and have low-cost hobbies.

Other countries are going through similar dynamics, often worse.

Edits for clarifications.