The UK system is somewhat better - in that most (secondary) teachers do understand their subject reasonably well.
It's just as bad in that any decent teachers soon want to leave ... :-(
My daughter is typical. She did a degree in Music Theatre, before deciding to go into teaching. She then did a PGCE (Post-Graduate Certificate in Education) which was largely spent in the classroom, before getting a job as a teacher. Six years on she is a very good "Head of Specialty", is getting really fed up, and is thinking of leaving her school - and possibly leaving teaching - in a few years time.
Her fiance is also a teacher, also fed up, and also wanting to leave ...
("Head of Specialty" - most schools in the UK specialise in something, be it maths, science, arts, whatever. She is head of her school's specialty department - performing arts.)
(The alternative to a PGCE is a Graduate Trainee - again, get a job as a teacher in a school and get trained on the job. Most of these people come from industry and teaching is not their first job.)