You can learn something parrot fashion, but I can't think of a word for the sort of person you describe.
Interested in Language
As the title says what's the saying in English for someone who knows everything by heart about any specific issue but doesn't actually grasp the main idea, logic and concept of it? Even doesn't get the idea for what purpose it serve and how to tackle on different occurences of problem.
Just adapt an existing concept and mould the context around it in order to get close to the meaning that you need:
- Intellectual drone;
- Armchair intellectual.