“If I have only acquired 500 unique words by the end of the year, I will not have made any appreciable progress, because I would then need about 15 years to reach the required amount of words to read authentic native texts, which is around 8000 words.”
It just doesn´t work that way. Every word you learn makes learning new words easier. (because of roots, compound words, better listening comprehension, more familiarity with the Russian alphabet and whatnot)
What´s your definition of “word” by the way? And why do you think that you need 8000 words to read an “authentic text”?
And what´s “authentic”? Tolstoi? A speech by Putin? The lyrics of a rap song?
I think that calculation is nonsense. Wait! It´s worse than nonsense. It´s logical sounding, discouraging nonsense.
“oh and memorizing lists of words devoid of any kind of context is a very poor way to learn vocabulary…so I don’t use spaced repetition software.”
Type a sentence instead of a single word. Problem solved.
PS: This post might sound a little bit harsh, but I wrote it to help you 