Here are some tentative answers to this rather complex question:
- One could say that the sentence contains two mistakes and that it should be “It doesn’t come easily”. On the other hand, this is a perfectly clear, comprehensible sentence containing perfectly normal English words being arranged in a perfectly normal order in English. How right the sentence is becomes clear if we compare it with “Come don’t easily it”, which is really wrong, or with “Blubber ghastly if matter no”, which is perhaps even more wrong.
- In order to decide if the sentence is “wrong”, it may be useful to know how many native speakers are likely to produce such sentences, whether it is accepted in certain varieties of English, in which situation it was said and by whom. It would be considered more “wrong” if said by somebody in Parliament during an official speech (assuming that it isn’t said jocularly) but it would be considered less wrong if said by somebody in pub to a friend in casual conversation. In this particular case, the sentence is actually the title of a pop song, an indication that it is, at least to a certain extent, accepted by English speakers.
- The argument show that sentences, or at least these kinds of sentences, are not “wrong” by themselves but may only be considered “wrong ” by certain people in certain situations, so their being “wrong” depends on these people’s criteria. Linguists would probably consider this sentence quite “right”, although not corresponding to the present rules of Standard English.