I found many teachers turn down the great job offer because of the bad reviews online. Some teachers do some research online and read a fair amount of concerning reviews. They found Hagwon was on a website called "Hagwon blacklist".
I completely understand their concern. A lot of people only want to post about negative experiences while leaving out positive ones. What is important to keep in mind though is with any of these chain schools in Korea - LCI, Brighton, Wonderland, ECC, Reading Star, CDI, SLP, etc. They will have 30-150+ franchises around Korea - so they can be vastly different between them, so it's important to research the specific location. The textbooks and curriculum are the same, but the management is different because of different director.
We work really closely with SLP, ECC and JLS schools. But to help,we usually connect you with 1 or 2 native teachers at school, so you can ask any direct questions. Are you most concerned on not being paid, heavy workload, mean managers, etc? It's very important to be careful, but It is also ridiculous to believe what they say online.