Singlish is not about ungrammatical English. In fact, it is quite rude to correct another person's "imperfect" Engish. Many times before, we have seen the person doing the correction turning good English into bad English due to his poor command of the language.
The English-speaking world probably understands a Thai or an Indonesian speaking imperfect English. But the world will never understand Singlish because it is unintelligible. And in order for a foreigner to master Singlish, he/she first has to master non-standard Hokkein, Malay, etc. It's an impossible task.
The harsh fact is Singaporeans speak non-standard dialects and languages. It may have something to do with the genes.
Our Mandarin is equally atrocious, it is peppered with English words. The end results is that both the native Mandarin and English speaker cannot understand a Singaporean, at least not fully.