I think it is important to aim for native-speaker pronunciation.First of all,I think perfection is always a good goal in any aspect of language-learning.We aim for perfect grammar,so why not perfect pronunciation?
Second,the purpose of learning a language is to communicate with native-speakers or people from other parts of the world.The better my pronunciation is,the more easily they will be able to understand me.And I want people to understand me without any difficulty.
Third,English is now an international language and I would like to be part of that community.If my pronunciation is like a native-speaker's,I will blend into the community more naturally.I'll feel pleased if I am taken for a native-speaker.Even if I can't speak so well,I don't like to spoil the language by terrible pronunciation.
So learners should aim to speak English with a native-speaker pronunciation