RIP Wels and those parts of Vienna with percentages of non German speakers in the 80s.
And I'm not the kind of person that usually freaks out about inmigrants, but them not learning German or using it as their primary language is literally the worst thing that can happen and shows that their integration level is essencially nonexistent.
Austria shouldn't allow this. If you've lived in Austria your entire life, you must speak flawless German. Of course, first generation inmigrants should be excluded from this, anyone learning a language as an adult or even an older child will never be perfect native speakersand probably will always have an accent, even if it's a faint one.
But anyone born in Austria and living in Austria for their entire life must speak flawless native German, no exceptions. Same goes with any other country in Europe really.