Well, the accuracy of the network depends on a lot of different parameters so we are not always sure that the network will converge that is indeed true, however, I do not see any problem using an existing technology that works, make easy for normal people to use it and enjoy the benefits for it. Neural Networks aren't, indeed, a universal algorithm but they work pretty good so far in my opinion
Well, today no neural networks can't do things like creating new knowledge. I encourage you, however, to check out GAN's, Neural Networks that can produce new and original results, that is to say, they can generate faces and digits, which do not exist. Also, there are neural networks capable of producing music, poetry and using style transfer they are able to transfer painting styles. So, I think that the future looks promising for the area of Neural Networks, but there is still a lot of work to do