28 is the median age of starting a Ph.D. in Germany, you are by no means old and being a few years "behind" (which I don't think you are if you learned anything during your 3yoe soft skills, etc.) a small fraction of Ph.D. students does not matter when you consider how long of a carrier you have in front of you.

I worked as a Data Scientist before starting my Ph.D. and was bored with it which is why I started mine. If you think doing a Ph.D. excites you and/or you think it will open up more exciting jobs in the future do it! Else you can have a fine career with your current credentials.