Obviously, nothing is perfect.
Source: https://de.wikipedia.org/wiki/Abiturientenquote_und_Studiena...
All programs have requirements, to take a STEM program you need to have calculus, physics and similar from high school. If you don't have it there's generally a system to study for a year to pass those courses, allowing you to change track.
The entrance is then essentially. (Checked my program)
1. 66% based on high school grades
2. 34% on a SAT/ACT like test.
The test is different though, no essays or other subjective stuff. It essentially has two parts both multiple choice, one testing language and one testing logic. Score is assigned by bell curve of all takers. Generally not as good predictor of student suitability as grades but allows people who just barely passed high school due to lack of motivation, issues at home and similar to still have a chance getting into their dream career if they are smart enough.
You can generally with really high motivation study for the test and raise your score a bit, not hugely though, and having that motivation is another predictor for success studying so works itself out.
There are STRICT entrance requirement - basically tied to your Abitur or similar. This means big waitlists if you are not a top scoring (on Abitur). European systems DO have exams and they can be pretty high stakes for classes. There are lots of quotas - as should be obvious given the education is free.
"The remaining places not reserved for the aforementioned advanced quota groups are filled following the Abiturbestenquote, i.e. applicants with the best higher education entrance qualification grades, and Wartezeitquote, applicants with the highest amount of accumulated wait semesters. The admission criteria within the selection process of institutions of higher education (Auswahlverfahren der Hochschulen, AdH) are set by the universities and institutions themselves according to the respective state law and their own requirements. Therefore, the AdH is not an additional application and admission procedure, but only one of several quotas."
There used to be public graduation rankings, but they are no more.