I understand what you're saying. For me though, the statement is actually true. I don't really want to die, I just don't want to continue living under the circumstances (which are many) and it's highly unlikely that my life is going to improve to the point that I want to stay. Is it impossible? No, but like I said, very unlikely and I'm already exhausted to a point I didn't know was possible.
Everyone is different though. That statement isn't true for everyone. But even if it was, I still don't think it's a good argument against suicide. So what if it's just the pain that people want to end? Sometimes, that pain is permanent. Sometimes, that pain is far too intense for someone to go through, even if it isn't permanent and I don't think it's fair to tell someone it's not okay to die when they are being tortured every day, for who knows how long. A lot of people seem to understand that when a cancer patient refuses treatment, because the likelihood of success is far too slim and they'd rather spend the rest of their time as comfortable as possible then risk that for an outcome that's such a long shot.
I'd rather die now then be absolutely miserable for the next 10 years, on top of the 10 miserable years I've already lived. Even if I would have found happiness later in life if I hadn't died, so what? I won't be around to regret it.
Anyway, I DO understand what you're saying and I absolutely hate when people invalidate our own feelings and problems. I can't talk to most people about suicide, because it gets me too worked up. Most people simply can't understand what they've never dealt with and it seems like they have no interest in trying to understand. We're often taught to put ourselves in other people's shoes, but many have no idea how to really do that (or even want to). It's depressing AF.