Russia would first have to be a "normal country". It would need an educated populace and a non-extractive (manufacturing or services) economy. It suffers from both a resource curse and Dutch disease. It is difficult to form a middle class that's independent of state institutions and employment. It has poor demographics and brain drain. It has no independent elites (academics, journalists, judges, business people), so the only restorative force in the society is brutal punishment for non-alignment with a cult of personal power.

Even if Putin wanted to join the E.U., the economy, social structures and institutions, and uneducated voting populace wouldn't allow it to be stable enough to join.

Russia at this point can't even be a successful authoritarian state like China. It's hard to say that it will never be a democracy, but those with a memory of the 1990's find that idea traumatic. Looking far forward in time, eventually global oil independence and demographic decline may force economic reform.

It would need an educated populace

How do you measure that?