Well, there are ways around the language barrier, like pinging and using common terminology like "mia", "ss", etc. Just playing well in lane and sticking together mid and late game helps as well. This is much more manageable in ranked, as even the "BR" players (as you refer to them) have their elo at stake. In normal games, it's much harder to cope with the language barrier, I'm sure, but at the same time, you have nothing to lose in a normal game.
In my personal experience, Riot rarely paired me with premade/abundant BR's in one team. In most unfavorable cases, you'll have that one Spanish-speaking individual who only plays Annie mid, but that's no excuse for the other 4 players to not try to adapt and synergize with that.