I have an explainer here: How Competitive Skill Rating Works (Season 14).
If you are below diamond, your SR gain/loss is affected by your statistical performance, which can make it take more or less games to climb up.
If your performance is average, you mathematically only need a win rate slightly over 50% to climb up, but if your win rate is 51% it will take almost an eternity to get anywhere. I don’t really feel like I’m climbing at a decent rate unless my win rate is around 60%.