I hear some people here and there blame Koreans for using English loanwords or for using "bad" English in sign boards and speaking "bad" English.
Regarding English loanwords in Korean, it has been argued that the words do no have the same meaning in English, that English and Korean are unrelated languages therefore Korean should borrow or use words that are only derived from related languages.
I would like to start by saying that approximately 65% Korean words are derived from old Chinese. Chinese and Korean are not related languages, and are as unrelated as English and Korean. Chinese is an analytical language, a language in which each syllable has a meaning. Korean however is an agglutinative language, a language where chunks of words "stick" together to form longer words or grammatical elements. Therefore in Chinese, a word like 알밥 (a dish made up of rice and fish eggs) could be broken down into two words, 알 and 밥, meaning eggs and rice. However, a word like 하나, which is a Korean word meaning one, can not be broken down into syllables. Most importantly, Chinese is a Sinitic language which evolved in China, while Korean is most probably an Altaic language which evolved in a part of what is today Russia.
*There are a lot of French loanwords in English, yet French and English are only very distantly related... both are Indo-European languages, but French is a Romance language and English a Germanic language. There are lots of Yiddish loanwords in Hebrew yet to the surprise of many Yiddish and Hebrew are not related at all. Actually, Yiddish is related to English as they are both Germanic languages, whereas Hebrew is a Semitic language of the larger Afro-Asiatic family of languages. Japanese and Korean are related but both languages are not related to Chinese. Therefore some languages can loanwords from other languages without impairing the language.
Being Jewish or having slanted eyes does not automatically qualify people to speak related languages.
As for "incorrect" use of English, we first have to define what the "correct" form of English is. British English? American English? What about inner city English or Ebonics? Politicians widely agree on the fact that "correct" English is upper middle class White English, because they are usually themselves upper middle class white people. However, linguists agree that all forms of English spoken by people as their first language are correct forms of English. Konglish may not be a correct form of English but it certainly is a correct form of Konglish.
However I must say that since Korean people usually read Korean signboards and that only those who don't speak Korean read signboards in English, Koreans should write their signboard in English rather than Konglish. But, hiring native English speakers to proofread Konglish is an investment that authorities are not willing to make. After all still relatively few foreigners come to Korea, and even fewer speak English.
Let's just say that according to the Korea Immigration Office Website, out of 873,000 foreigners registered in Korea, 806,000 are from Asian countries, a large majority from countries where English is not even spoken as a second language. So the sign boards in English are for the minority of People who are likely to speak English as their first or second language. If I had to write signboard for 50,000 people out of a population of 48 million, I would not put too much effort into them. With 350,000 of the foreigners, or almost half, being Chinese, there should perhaps be more signboards in Chinese. However, it is important for Koreans not to offend their English speaking investors, which is probably why there are English signboards in the first place.