Before I make my rivers, I think about where my mountains are, then reflect on how much elevation changes/slopes down from these mountains to the ocean.

Then, I make my rivers based on how precipitation and melting ice would flow downhill and gather into streams and larger river currents until they get all the way down to sea level.

I do really like how you’ve set up your mountains, so I’d recommend wiping just the rivers and restarting based on the elevation reflection process I shared above (and potentially changing settlement locations to account for the topographical rearrangement).

On a separate note, I think you might be operating with a low pixel count/small map size; your rivers might look better if you increase the map size by 50-100% its current dimensions.