People posting their PI on their own in public is however not something the GDPR really covers and so would not affect a forum operator. Leaking users email addresses is another thing of course, but was undesirable before there was GDPR. (Though it might be totally possible to run a forum without requiring email if one is really worried)
You are not wrong though that running forums or any website with user generated content is becoming increasingly difficult for individuals, though the real culprits here on EU level are the recent copyright reform which requires you to remove infringing content quickly and the upcoming Anti-Terror regulation which requires removing content in one hour. Though it might be true, that many of these laws might be toothless against individuals or non-profits, even though they do not specially exclude them. But it really seems lawmakers don't think much of the internet beyond facebook, twitter and google.
You are not wrong though that running forums or any website with user generated content is becoming increasingly difficult for individuals, though the real culprits here on EU level are the recent copyright reform which requires you to remove infringing content quickly and the upcoming Anti-Terror regulation which requires removing content in one hour. Though it might be true, that many of these laws might be toothless against individuals or non-profits, even though they do not specially exclude them. But it really seems lawmakers don't think much of the internet beyond facebook, twitter and google.