I don't know how religious Russians & co are though; maybe they are just ritualistic and simply like the church and what it represents, without having muсh faith.
Well, people are different, but those who regularly go to the church are really religious in general. There is no tradition of going to the church in Russia because religion was heavily oppressed during the soviet period. And it is not easy to stand for hours in the church.
The number of priests grew several times in the last 20 years, that's why there are many young priests. Probably there are fewer churches in Russia than in Western Europe.
Russian Orthodox Church uses Church Slovenian (derived from Old Bulgarian) in services.