There’s no “one formula fits us all” for education – I dare to say no one universal formula exists for any problem on earth.
One duty of a teacher is to impact knowledge to all their students, (keyword: ALL) so when a teacher makes a comment like “if half of the class passes then I’m justified“, it is a sign negligence of duty on the teacher’s part. Every student can understand anything – depends on how you explain it.
We might need to take a cue from the Finnish teaching model where teachers make sure their students understand by seeking various teaching techniques from teachers across the country.
To teach and not infuse one or two distinct practical examples is a terrible teaching technique. The idea is to make the student understand to the extent he/she can teach someone else in his/her own words. Without proper explanation, the student is better of reading from textbooks.
Finally, teaching is not a ” last resort job”. It’s in the same bracket as being a doctor, engineer, lawyer, programmer, strategist, etc – If you don’t have a knack for it, your services are not needed.