Imageboards have had a pretty large effect on my life.
I've met the majority of my partners through imageboards, ended up falling into the ratsphere because of people I met on imageboards, I mean I could make a very extensive list of all the positive things that imageboards have exposed me to.
At the same time I've also spent a huge amount of my youth being exposed and desensitized to racism, extreme pornography, bigotry, all kinds of conspiracy theories, various time-wasting addictions, self-reinforcing negative feedback loops and poisonous ideaologies. I'd like to say that I came out of all this fairly well adjusted, but what the fuck does a well adjusted person look like in [current year] anyway?
Overall I feel like it's been positive, but I hear from enough people that they've found imageboards horrifying and useless that I consider my experience maybe not representative. I have no issue glossing over posts that don't interest me or seem obnoxious. I guess not everyone can do that effortlessly.