I agree 100% with Propp. Starting Russian is much harder than starting English.

The final stages of learning good English involve:

-developing the ability to use the full range of tenses accurately. Most students can do this eventually.

-developing some kind of unconscious internal rule set (with thousands of exceptions) telling you when to use articles and which to use. Non-natives never completely master this except in very special circumstances.

-developing a feel for and mastery of phrasal verbs; perhaps the hardest thing of all.

Of course one must also get to grips with idioms, connotation, collocation, register and perhaps some forms of slang, but that's true in any language.

On the subject of history, well, I'm no historian, but I would have thought that the development of the printing press must have had a big effect on the stabilization of the language. The internet may be having a similar effect on a global scale today