Why tf can’t I get out of diamond?

I don’t get it. I lose 90% of my matches in diamond and it’s an obvious loss from the start. Like it’s very clear our team is going to lose within the first few seconds of a match and losing 10 games in a row repeatedly is just not even slightly fun. I’m used to having 0 deaths and now I can’t do anything. It doesn’t matter. Why is this happening?