Very interesting analysis. As a polyglot, yet a person who speaks fluently only single foreign language (my German has still many flaws, my Russian and Ukrainian is strong passive way, French is only rudimentary)I know how hard it is to master foreign languages expertise. It is better to know single foreign language but on high level of proficiency than to know many languages on maximum intermediate level.
One should master every single language, including the native one, through the whole life. All of languages are still in the state of development. And it is better to have the contact with foreign language on the daily basis.
Due to the fact that English is a lingua franca, it is not a problem. Harder case is with less popular, mostly local languages. For me, it is natural to learn languages of the neighbouring country/ies. So, for a Pole, it is obvious to have at least rudimentary, passive knowledge of German, Russian. Due to the fact that many Ukrainians live currently in Poland, it is not hard to hear Ukrainian or Russian on the street. For me, it is not a problem, for most of young Poles who are not able to differ between Ukrainian and Russian (or even Slovak and Czech which for many sound the same)it is out of this world case.
So, learn languages, people.