It is possible, I suppose – if you know nothing and/or care nothing about the real-life Tennessee Williams or Marlon Brando – to find “Kowalski” a fully satisfying theatrical experience. This would largely be because of Brandon Flynn. Flynn is now best-known for his role in the TV series “13 Reasons Why,” but I remember him vividly portraying the kidnapped child at the center of “Kid Victory,” the 2017 John Kander and Greg Pierce musical. Flynn’s performance moved us to identify with his character’s suffering, and joy, and confusion.The writing in “Kowalski” doesn’t get inside the characters in the same way, and when Flynn first appears, my main reaction was to size him up based on how accurately his voice and manner and appearance correlated to the real Brando. But by the end, his performance seemed less an impersonation, and more an argument for the power of a magnetic actor.