Lived experience is so important! I think it helps people who don't really know much about a certain to issue to understand that behind any issue there is a human being, and hearing from people about their lived experience can really deepen and enrich our understanding of those issues.
I've done some work as someone with lived experience of mental illness, and having a parent with a mental illness, and not only has it been really rewarding for me, I've had people come up to me afterwards and share some of their stories and thank me for being open with my experiences, which is beautiful.
In terms of helpful/unhelpful, I think rumination on the negative aspects of the issues without any exploration of the potential to move forward/improve can be quite negative. Also, sharing lived experience without balancing it with adequate self-care can be really draining and is probably something to be avoided.