Years ago when I started teaching English in Korea things were very odd. No one really knew what to do. Basically, go in to the class and some how "teach". There was no training 20 years ago. English academies where everywhere. Teachers from the so called native English speaking countries were a very common site.
Today some things have stayed the same while other things have changed dramatically. Way back in the day the way of teaching a class was so simple and straight forward. This caused many issues as teachers who did not really respect the job would end up boring students. This stayed like this for many years. Teachers could get a visa very easily and cheaply. So you have a industry where teachers rarely stayed longer than one or two years at one location. They could get work papers easily. The days of the visa run to Japan comes to mind.
Today when teaching we have to do many other things that...well take away from teaching. This is due to the growing influence of Korean mothers. They are not experts in linguistics yet they wield power. They typically control the money in a Korean household. So when groups of moms get together ideas pop up. Those ideas make their way into the classroom. Sometimes these new ideas come from educational channels on TV or popular trends in Seoul. These trends are often short lived. I remember the flash card trend. When people who are not well versed in a field wield power over said field...it is unsustainable.
Lets go back to teachers. There are more qualified teachers in Korea than ever before. The total number of e-2 visa English teachers has decreased though. Rules have tightened, teachers and employers have to use 1 year visas. This means that once a year your life will pause, while you sort your papers out to stay one more year. The changes to teaching visas is a very good thing in many ways. People with criminal records would run to Asia and work. Thus escaping the stigma of a criminal charge on their record. Back in the day no background checks were run. I remember when that change was implemented. It caused a panic!
Visa fees have increased, durations have not changed despite many people staying longer at stable, very well run schools. People who really want to live in South Korea are having a hard time these days. To gain permanent residency status is based a point system, not how many years you have lived in the country paying taxes, not causing problems. This is not sustainable. I have seen so many long term teachers 5-15 years in Korea throw in the towel.
Academy owners are under a crazy amount of stress. People steal ideas (this actually happened to us in Gunsan) and curriculum from competitors. I have seen this happen in Gunsan SO many times. Owners have to deal with unreasonable demands from parents. I will not go into detail here lets just say it makes Korean teachers, and owners lives miserable. This leads to burn out. Which means...it is not something that can survive long term. Mothers in Korea seem to think that piling homework on their children is the answer.
I could rant on for hours but I do not see ESL surviving in the form that it is today for maybe another 10 years. Heck perhaps 5 years from now there will some major change. People have a breaking point. I read the diary of one student. That student stated that they only enjoyed ONE day of the week. ONE DAY. When I was a child I enjoyed EVERYDAY, well except Monday's. Even today I live for everyday. I feel that a change is coming.