We know that English is not the native language of the asker. But, at the same time, I wonder how helpful it would be to explain English concepts in English. Understanding English with English words requires some advanced English knowledge. For people who are less than advanced in English, we may request them to add their native language, and we may explain the concept in the native language of the speaker.
It's a tempting idea, but it wouldn't work at all.
First, how are we going to get enough native speakers of various languages that also speak English well to answer questions? Even the major ones, like Hindi, would have a lot of trouble, since most of the top answerers don't know those languages. Indeed, quite a few of them don't know any language but English. Cutting the answering pool down to 1/5 its size is bad enough, but 1/20 or 1/100 is much worse.
Second, how are we going to get enough good voters to determine which answers are good and bad? We have some trouble as it is getting enough voting on most posts, so turning a post that might, today, get +4 votes into one that none of those four upvoters can understand is not progress. Without score-based sorting, there's little value to Stack Exchange that a forum couldn't provide.
Third, posts in another language can't be effectively moderated. This is actually really bad, since a lot of low-quality answers, especially, would lie around without enough voters to notice their problems and do something. What do you do when someone posts "thanks, that answer really helped me!" in a language spoken by only two users that have access to low-quality post review to delete it? (The potential for spam to pop up and stick around a lot longer is also quite painful.)
Fourth, the earlier stages of language learning don't benefit nearly as much from the type of help Q&A posts can provide. That's where textbooks, individual tutoring, audio samples, and so forth are much more helpful.
For comparison, consider Stack Overflow, which gets somewhere around 1500 times as much activity as ELL. SO has had to move very slowly in its internationalization efforts, starting up sites one by one for specific languages that have a lot of experienced and active users. To be fair, a lot of the extra scale that SO has is taken up by the enormous tag fragmentation among different computer languages and environments. Even so, we would need to do the same thing, which means effectively writing up a proposal on Area 51 for "ELL for beginning Hindi speakers" (or whatever) and then working through the whole process of getting that launched. That's a very ambitious project, but it might conceivably work.
Just opening the floodgates and allowing anyone to use their native language to ask about English, all on the same site? That wouldn't.