I would like to supplement some more comments:
First: machines are artifacts created by humans. That is, we humans had some goal in mind and we decided to create an artifact that we could use as a means to achieve it. This definition imposes no restriction on what any machine can or can not do. Reiterating, it states that machines are objects created by humans to achieve some goal. I speculate that many people think that machines have some limitation based on a superficial generalization that they made of their own common experiences. They realized that machines such as blender, cars and lawn mowers had some "limitations" and generalized this as a "limitation" of all machines.
Second: we do not know how human language actually works, yet this is not an argument against the idea that machines can learn human language. If we knew how human language works it would be possible to say with certainty whether it is possible or not to build a Turing Machine that understands human language. The interesting thing is that even if we think hypothetically in the case that the Turing Machine is not able to compute the human language, it's not enough for us to build a machine that is more powerful than the Turing Machine to process the language. We have good reason to believe that the Turing machine can understand human language. I will not discuss the reasons in this text, but what I find most important is not to confuse what computers do today with what they can actually do. What computers do today depends on the implementations of engineering. There are many things that can be done with computers but we still do not know how to implement them concretely.
Third: many people find that showing complications in language is a barrier for a computer to understand the human language. The right question in this situation would be: why would this be a problem? What prevents these particularities from being treated? Critics have to be able to answer these questions.
Fourth: I would like to add an historical note. Many people think that computers are just machines, but what they do not know is that the concept of computing was created to capture the mechanism that we humans use to perform mathematical accounts. Because at the time that Turing defined computing those who did computing were people. What's amazing about this definition is that it's so good that you can even build machines with it, which is why we call it the Turing Machine. The fact that it is possible to build a machine to perform computations clearly demonstrates the power of the theory. Because computers have been a success and the history of computing is not widely publicized, people think that computing has only come with machines.