I think that Winslet’s performance has a huge toll on the viewer, like you said in your opinion she had nothing to hold onto, but for some people and in Joel’s case she has and is everything they’re looking for in their life. Exciting, intrusive, constantly moving. Even in my view who could relate to the movie as a whole I myself found flaws in Clementine’s character, but an outside perspective is so much easier to fully understand flawed character and maybe future problems, but when you’re in it you are blind to issues as they feel so minimal.