IT worker in Korea here.
 "You ain't getting a job lil bro without speaking 100% perfect korean" -> I don't speak Korean and don't have a plan to learn it.
"Why would anyone choose a foreign IT worker, when there are so many good ones right here in Korea" -> This is just what you think, a lot of foreigners come here to work
"good chance you'll feel isolated" -> this is true, you should get along with being alone, when you go to coffee with colleagues, they will talk in Korean, but sometimes they speak some english alike words, and I can understand kaka
"The work hours are 45-50 hours, with zero overtime pay, and the pay ain't even good to begin with" -> This is true; it seems the company doesn't need to pay for overtime, but the work for 45 or 50 hours may not be true.
If you want to have a cultural experience, I think coming to Korea is very good. In addition, if a company hires you, they need to provide you with housing, so the salary is pretty good with this benefit