Golf instruction for the most part is much improved over the years. I gave my first lesson as a golf professional in 1971 and wish I could find that young man and refund his payment with damages. Two main reasons for this improvement.
First, the education programs have improved significantly, starting with Michael Hebron who created a Summit in Dallas in 1988. The PGA of America took this program over and has held a major Summit every two years since. Loren Anderson also has held numerous multi day events each year for 20 years. The result is sharing and educating instructors to improve their skills.
The other improvement was in technology. Video especially has taken a lot of guesswork out of instruction and made teachers much better.
There are still instructors who do not keep learning and using these assets, but there are now a lot more very good teachers.