I think one can improve their command of a language with practice, as you say. If they don't encounter it in their day to day life, they can try and find ways to consume content in their target language [reading, watching, listening, interacting].
As an example, English is my fifth language. Do I use it in my physical day to day life in the country I am in? Not really. However, our internal communications are all in English (code, comments, Slack conversations, GitLab issues and comments, documentation, emails, pretty much everything).
The content I consume is mainly in English as well: talks, movies, books, articles, etc.
This can dramatically improve both your comprehension and your production. You can take a look at Stephen Krashen's work on language acquisition, it's interesting and matches my experience with languages (confirmation bias).
You provide some arguments in the text, but without sources; they are also contradictory and very vague. Dyslexia is not lack of reading comprehension, it's a specific medical diagnosis.
Please try to phrase your submissions in a way that states a clear point / question.