It might be rudimentary, but I wouldn't say you're wrong.

Alternatively, pick up but answer the phone only with the word "Yes?", "Speak" or "You may proceed" (preceded by 'this line is now secure').

Then, when they ask "who is this?" answer that "if you don't know, you have the wrong number" and that "this call is currently being traced, pending review of a 'military tribunal'."

Do this with the flattest intonation you can manage.

That tends to get to them.

My SIM provider has the option to not even route unknown callers to my device. Not that I get any, but just in case, even if it is not that common in Germany.

What some family of mine had to go through was social engineering harassment calls with some BS reasoning to get them to say "Yes"/"I agree" or something like that

Recently there were recruiters on LinkedIn freaking out that when they called someone, they would answer with "Hello?" and the recruiter thinks they're too good to be greeted with that.