A saddle that's too large and soft can cause problems.
A soft saddle is OK for short rides, but for longer rides a firm, or even hard, saddle is better.
Your weight should be taken by your sit bones (ischial tuberosities, as felt when sitting on a wooden stool or step that's below knee height).
If your saddle is too soft, the bones just sink in, and the weight is taken by the surrounding soft tissue, which can, especially if the saddle is wide relative to your pelvis, result in the blood vessels than are meant to be keeping your legs supplied getting squashed flat, which results in pain when you do much work.
A hard saddle can result in what feels like bruising of the sit bones when you first start cycling, but once you've got over it, it doesn't repeat, at least unless you stop cycling altogether for a couple of years.
The standard set up for saddle height is so that your leg is straight when your heel is on the pedal (socks or thin heel shoes only), and your pelvis doesn't rock from side to side if you pedal backwards with both heels.