There are some problems that just venting can help, but when it comes to depression and suicidal thoughts, talking alone doesn't help me. When I talk about depression, I only do enough talking to let the people in my life know how I'm feeling. The thing that actually helps is their actions following the talk, such as giving physical comfort, offering activities that cheer me up, or giving me more space.
It's not just a "you" problem. It could be that the people you're talking to don't know how to handle that kind of discussion. Even if they're being as supportive as possible, it's hard to make a depressed/suicidal person feel "seen," and making someone feel "seen" varies from person to person. The people you're talking to might also be dismissive, inattentive, or trying to solve your problems instead of just listening. Being a "fixer" often backfires in these conversations, as it just makes the depressed person feel bad for not being able to already fix their situation (in my experience).
If your main goal is to be understood from talking about shitty experiences, I think this forum and other places like it is the best avenue for that. Average people don't understand what you're going through. Conversation on here or group therapy might be helpful in that regard (be careful what you say in therapy, though).
If your main goal is to alleviate your shitty feelings, it's a lot tougher. Not everyone gains comfort solely from being understood or listened to. Most people are not good at talking through mental health and emotions with suicidal people. When I talk with the people I love about my emotions, I don't always feel better. Sometimes I feel much worse.
It's not your fault that talking isn't the best therapy for you. Talking through your emotions is a skill that's hard to hone, especially when all your emotions are painful. It could be that you haven't found someone you can speak with safely, the people around you aren't well-equipped to help you, or talking just doesn't do much for you at all. I'm sorry you're having so much trouble finding relief. I hope you can figure something out to feel a little better.