First of all, thank you for being an active user of Russian SE.
As of your question. The questions that you've described - asking translation of some particular phrase heard in movies, songs, seen somewhere etc. - are de-facto in the gray zone of off-topic on all language-dedicated SE sites. There were reasons for this.
For instance, our colleagues from English SE had decided that meme translations are most likely off-topic. Let me cite:
Most internet memes, like any particular cultural artifact, popped out
of some narrow situation that was then shared and other people seemed
to like it and continued sharing. Sometimes they are language based,
but for the most part the hook is cultural.
The same about song/poetry interptetations. The same about single-word requests.
The same about many things actually.
So, answering one part of your question - if you feel that some questions are off-topic and do not belong here, than just flag such questions, and moderators always take a look.
Answering another part of you question (ant to @Dmitry Alexandrov as well) - let me indeed apologize and acknowledge that some of deletions I've made are dubious. Indeed, we can close question as off-topic and not neceserily delete it - deletions are for content that's by definition can not be upvoted here - spam, obvious off-top etc.
Also, we can create a question on meta "What quesions are on-topic and off-topic here" just like a similar question on English SE and see how it goes.