We have this in Austria but if you are dedicated to take the lower school paths and later decided to get extra education to go the Uni, there's nothing that stops you. There's nothing unusual in a mid-20 taking evening school and going to uni two or three year. And not just that, if you dropped out with nothing at all, evening school allows you to get even the lowest ranking of the three paths: Hauptschulabschluss. The cost for you? Nothing!

When you have finished your Hauptschule or Realschule (lowest and mid path) you usually start a job but part-time you also go to a job-school (Berufsschule) where you learn more specific things that are useful for your job. This dual-education works great and is being exported to other countries where german manufacturers get active but don't find the skilled workers they are used to.

It's not as cut throat as you make it sound. People who go to "practical" schools can always switch back. I lived in Germany and have friends who got Bachelor's degree at 35+. Another good reason to make it affordable is that people will always have options.