No shit mindlessly using bloodthirst will get you killed. There are definitely times where you can put yourself at a huge disadvantage using bloodthirst, such as fighting a skilled high-level summoner or when dealing with someone with similarly overpowered cabal abilities (a/b/sed scion?). That doesn't really change the fact that it takes very little skill to win fights with bloodthirst, especially when you entwine them first. And fact of the matter is, most people don't run combos designed specifically to counter RBWs.

I could come up with dozens of different scenarios where thirst could really get the villager killed, but most of them involve either 1) the villager being stupid or 2) the opponent being either really overpowered or coming with a gang, in which case the villager is usually dead anyway.