I’m telling you that Bran’s mistake was preventable if Bloodraven had tried to protect Bran rather than exploit him lmao if he had Bran’s interests in mind than Bran would have known what to do and what not to do.
In addition BR has been showing Bran visions he knows he’ll like, visions that have to do with his family and don’t have dangerous characters. Only in the recent episode did he show more pivotal moments like the Children of the Forest creating whitewalkers, and even then BR clammed up and didn’t think to be like “okay, if you run into one of these guys in a vision, get the hell out or at least don’t get touched”.
Bloodraven, as I have been saying, kept Bran in the dark on purpose and allowed Bran to think that these visions were safe (as long as he didn’t stay too long). No one had ever interacted with Bran in them before; how was he supposed to know that the Night’s King was different?
A simple “Bran, don’t do this alone, because if the Night’s King finds you, he will mark you and our protections will be broken.”
Bloodraven did not do this.
Bran did make a mistake in his childish curiosity and quest for more about his family. But, as @lyannas said, Bloodraven purposefully kept Bran in the dark, and spoke in half-truths and riddles.